An aldehyde (pronounced /ˈældɨhaɪd/) is an organic compound containing a formyl group.

This functional group, with the structure R-CHO, consists of a carbonyl centre bonded

tohydrogen and an R group. [1] The group without R is called the aldehyde group or formyl

group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon

skeleton rather than between two carbon atoms. Aldehydes are common in organic chemistry.

Many fragrances are aldehydes.

Contents

 [hide]

1   Structure and bonding

2   Nomenclature

o 2.1   IUPAC names for

aldehydes

o 2.2   Etymology

3   Physical properties and

characterization

4   Applications and occurrence

o 4.1   Naturally occurring

aldehydes

5   Synthesis

o 5.1   Oxidative routes

o 5.2   Specialty methods

6   Common reactions

o 6.1   Reduction

o 6.2   Oxidation

o 6.3   Nucleophilic addition

reactions

6.3.1   Oxygen

nucleophiles

6.3.2   Nitrogen

nucleophiles

6.3.3   Carbon

nucleophiles

o 6.4   More complex reactions

7   Examples of aldehydes

8   Related compounds

9   See also

10   External links

11   References

[edit]Structure and bonding

Aldehydes feature an sp2-hybridized, planar carbon center that is connected by a double bond

to oxygen and a single bond to hydrogen. The C-H bond is not acidic. Owing to resonance

stabilization of the conjugate base, an α-hydrogen in an aldehyde is far more acidic with

a pKa near 17[2], than a C-H bond in a typical alkane, with a pKa in the 30's. This acidification is

attributed to (i) the electron-withdrawing quality of the formyl center and (ii) the fact that the

conjugate base, an enolate anion, delocalizes its negative charge. Related to (i), the aldehyde

group is somewhat polar.

Aldehydes (except formaldehyde) can exist in either the keto or the enol tautomer. Keto-enol

tautomerism is catalyzed by either acid or base. Usually the enol is the minority tautomer, but it

is more reactive.

[edit]Nomenclature

[edit]IUPAC names for aldehydes

The common names for aldehydes do not strictly follow official guidelines, such as those

recommended by IUPAC but these rules are useful. IUPAC prescribes the following

nomenclature for aldehydes:[3][4][5]

1. Acyclic aliphatic aldehydes are named as derivatives of the longest carbon chain

containing the aldehyde group. Thus, HCHO is named as a derivative of methane, and

CH3CH2CH2CHO is named as a derivative of butane. The name is formed by changing

the suffix -e of the parent alkane to -al, so that HCHO is named methanal, and

CH3CH2CH2CHO is named butanal.

2. In other cases, such as when a -CHO group is attached to a ring, the suffix -

carbaldehyde may be used. Thus, C6H11CHO is known as cyclohexanecarbaldehyde. If

the presence of another functional group demands the use of a suffix, the aldehyde

group is named with the prefix formyl-. This prefix is preferred to methanoyl-.

3. If the compound is a natural product or a carboxylic acid, the prefix oxo- may be used to

indicate which carbon atom is part of the aldehyde group; for example, CHOCH2COOH

is named 3-oxopropanoic acid.

4. If replacing the aldehyde group with a carboxyl group (-COOH) would yield a carboxylic

acid with a trivial name, the aldehyde may be named by replacing the suffix -ic acid or -

oic acid in this trivial name by -aldehyde.

[edit]Etymology

Formic acid

The word aldehyde was coined by Justus von Liebig as a contraction of the

Latin alcohol dehydrogenatus (dehydrogenated alcohol).[6] In the past, aldehydes were

sometimes named after the corresponding alcohols, for example, vinous

aldehyde for acetaldehyde. (Vinous is from Latin vinum = wine (the traditional source

of ethanol), cognate with vinyl.)

The term formyl group is derived from the Latin and/or Italian word formica = ant. This word can

be recognized in the simplest aldehyde, formaldehyde (methanal), and in the simplest

carboxylic acid, formic acid (methanoic acid, an acid, but also an aldehyde).

[edit]Physical properties and characterization

Aldehydes have properties that are diverse and that depend on the remainder of the molecule.

Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so.

The volatile aldehydes have pungent odors. Aldehydes degrade in air via the process

of autoxidation.

The two aldehydes of greatest importance in industry, formaldehyde and acetaldehyde, have

complicated behavior because of their tendency to oligomerize or polymerize. They also tend to

hydrate, forming the geminal diol. The oligomers/polymers and the hydrates exist in equilibrium

with the parent aldehyde.

Aldehydes are readily identified by spectroscopic methods. Using IR spectroscopy, they display

a strong νCO band near 1700 cm−1. In their 1H NMR spectra, the formyl hydrogen center absorbs

near δ9, which is a distinctive part of the spectrum. This signal shows the characteristic coupling

to any protons on the alpha carbon.

[edit]Applications and occurrence

Important aldehydes and related compounds. The aldehyde group (or formyl group) is colored red. From the left:

(1) formaldehyde and (2) its trimer 1,3,5-trioxane, (3)acetaldehyde and (4) its enol vinyl alcohol,

(5) glucose (pyranose form as α-D-glucopyranose), (6) the flavorant cinnamaldehyde, (7) the visual pigment retinal,

and (8) the vitamin pyridoxal.

[edit]Naturally occurring aldehydes

Traces of many aldehydes are found in essential oils and often contribute to their favorable

odors, e.g. cinnamaldehyde, cilantro, and vanillin. Possibly because of the high reactivity of the

formyl group, aldehydes are not common in several of the natural building blocks - amino acids,

nucleic acids, lipids. Most sugars, however, are derivatives of aldehydes. These "aldoses" exist

as hemiacetals, a sort of masked form of the parent aldehyde. For example, in aqueous solution

only a tiny fraction of glucose exists as the aldehyde.

[edit]Synthesis

There are several methods for preparing aldehydes,[7] but the dominant technology

is hydroformylation.[8] Illustrative is the generation of butyraldehyde by hydroformylation

of propene:

H2 + CO + CH3CH=CH2 → CH3CH2CH2CHO

[edit]Oxidative routes

Aldehydes are commonly generated by alcohol oxidation. In industry, formaldehyde is

produced on a large scale by oxidation of methanol. Oxygen is the reagent of choice, being

"green" and cheap. In the laboratory, more specialized oxidizing agents are used, but

chromium(VI) reagents are popular. Oxidation can be achieved by heating the alcohol with

an acidified solution of potassium dichromate. In this case, excess dichromate will further

oxidize the aldehyde to a carboxylic acid, so either the aldehyde is distilled out as it forms

(if volatile) or milder reagents such as PCC are used.[9]

[O] + CH3(CH2)9OH → CH3(CH2)8CHO + H2O

Oxidation of primary alcohols to form aldehydes and can be achieved under milder,

chromium-free conditions by employing methods or reagents such as IBX acid, Dess-

Martin periodinane, Swern oxidation,TEMPO, or the Oppenauer oxidation.

Another oxidation route significant in industry is the Wacker process, whereby

ethylene is oxidized to acetaldehyde in the presence of copper and palladium

catalysts (acetaldehyde is also produced on a large scale by the hydration of

acetylene).

[edit]Specialty methodsReaction name

Substrate Comment

Ozonolysis alkene ozonolysis of non-fully-substituted alkenes yield aldehydes upon reductive work-up.

Organic reduction

esterReduction of an ester with diisobutylaluminium hydride (DIBAL-H) or sodium aluminium hydride

Rosenmund reaction

acid chloride or using lithium tri-t-butoxyaluminium hydride (LiAlH(OtBu)3).

Wittig reaction ketone reagent methoxymethylenetriphenylphosphine in a modified Wittig reaction.

Formylation reactions

nucleophilic arenes

various reactions for example the Vilsmeier-Haack reaction

Nef reaction Nitro compound

Zincke reaction pyridines Zincke aldehydes form in a variation

Stephen aldehyde synthesis

nitrilesreagents tin(II) chloride and hydrochloric acid.

Meyers synthesis

oxazineoxazine hydrolysis

McFadyen-Stevens reaction

hydrazideis a base-catalyzed thermal decomposition of acylsulfonylhydrazides

[edit]Common reactions

Aldehydes are highly reactive and participate in many reactions.[7]" From the industrial

perspective, important reactions are condensations, e.g. to prepare plasticizers and

polyols, and reduction to produce alcohols, especially "oxo-alcohols." From the

biological perspective, the key reactions involve addition of nucleophiles to the formyl

carbon in the formation of imines (oxidative deamination) and hemiacetals (structures

of aldose sugars).[7]

[edit]ReductionMain article: Aldehyde reduction

The formyl group can be readily reduced to a primary alcohol (-CH2OH). Typically this

conversion is accomplished by catalytic hydrogenation either directly or by transfer

hydrogenation. Stoichiometric reductions are also popular, as can be effected

with sodium borohydride.

[edit]Oxidation

The formyl group readily oxidizes to the corresponding carboxylic acid (-COOH). The

preferred oxidant in industry is oxygen or air. In the laboratory, popular oxidizing

agents include potassium permanganate, nitric acid, chromium(VI) oxide, and chromic

acid. The combination of manganese dioxide, cyanide, acetic acid and methanol will

convert the aldehyde to a methyl ester.[10]

Another oxidation reaction is the basis of the silver mirror test. In this test, an

aldehyde is treated with Tollens' reagent, which is prepared by adding a drop

of sodium hydroxide solution into silver nitrate solution to give a precipitate of silver(I)

oxide, and then adding just enough dilute ammonia solution to redissolve the

precipitate in aqueous ammonia to produce [Ag(NH3)2]+ complex. This reagent will

convert aldehydes to carboxylic acids without attacking carbon-carbon double-bonds.

The name silver mirror test arises because this reaction will produce a precipitate of

silver whose presence can be used to test for the presence of an aldehyde.

If the aldehyde cannot form an enolate (e.g., benzaldehyde), addition of strong base

induces the Cannizzaro reaction. This reaction results in disproportionation, producing

a mixture of alcohol and carboxylic acid.

[edit]Nucleophilic addition reactions

Nucleophiles add readily to the carbonyl group. In the product, the carbonyl carbon

becomes sp3 hybridized, being bonded to the nucleophile, and the oxygen center

becomes protonated:

RCHO + Nu- → RCH(Nu)O-

RCH(Nu)O- + H+ → RCH(Nu)OH

In many cases, a water molecule is removed after the addition takes place;

in this case, the reaction is classed as an addition-elimination or addition-

condensation reaction. There are many variations of nucleophilic addition

reactions.

[edit]Oxygen nucleophiles

In the acetalisation reaction, under acidic or basic conditions,

an alcohol adds to the carbonyl group and a proton is transferred to form

a hemiacetal. Under acidic conditions, the hemiacetal and the alcohol can

further react to form an acetal and water. Simple hemiacetals are usually

unstable, although cyclic ones such as glucose can be stable. Acetals are

stable, but revert to the aldehyde in the presence of acid. Aldehydes can

react with water to form hydrates, R-C(H)(OH)(OH). These diols are stable

when strong electron withdrawing groups are present, as in chloral hydrate.

The mechanism of formation is identical to hemiacetal formation.

[edit]Nitrogen nucleophiles

In alkylimino-de-oxo-bisubstitution, a primary or secondary amine adds to

the carbonyl group and a proton is transferred from the nitrogen to the

oxygen atom to create a carbinolamine. In the case of a primary amine, a

water molecule can be eliminated from the carbinolamine to yield an imine.

This reaction is catalyzed by acid. Hydroxylamine (NH2OH) can also add to

the carbonyl group. After the elimination of water, this will result in an oxime.

An ammonia derivative of the form H2NNR2 such as hydrazine (H2NNH2)

or 2,4-dinitrophenylhydrazine can also be the nucleophile and after the

elimination of water, this will result in the formation of a hydrazone. This

forms the basis of a test for aldehydes and ketones.

[edit]Carbon nucleophiles

The cyano group in HCN can add to the carbonyl group to

form cyanohydrins, R-C(H)(OH)(CN). In the Grignard reaction, a Grignard

reagent adds to the group, eventually yielding an alcohol with a substituted

group from the Grignard reagent. Related reactions are the Barbier

reaction and the Nozaki-Hiyama-Kishi reaction. In organostannane

addition tin replaces magnesium.

In the aldol reaction, the metal enolates of ketones, esters, amides,

and carboxylic acids will add to aldehydes to form β-hydroxycarbonyl

compounds (aldols). Acid or base-catalyzed dehydration will then lead to

α,β-unsaturated carbonyl compounds. The combination of these two steps

is known as the aldol condensation. The Prins reaction occurs when a

nucleophilic alkene or alkyne reacts with an aldehyde as electrophile. The

product of the Prins reaction varies with reaction conditions and substrates

employed.

[edit]More complex reactions

Reaction nameProduct

Comment

Wolff-Kishner reduction

alkane If an aldehyde is converted to a simple hydrazone (RCH=NHNH2) and this is heated with a base such as KOH, the terminal carbon is fully reduced to a methyl group. The Wolff-Kishner reaction may be performed as a one-pot reaction, giving the overall conversion RCH=O → RCH3.

Pinacol coupling reaction

diol with reducing agents such as magnesium

Wittig reaction alkene reagent an ylide

Takai reaction alkene diorganochromium reagent

Corey-Fuchs alkyne phosphine-dibromomethylene reagent

reactions

Ohira–Bestmann reaction

alkynereagent dimethyl (diazomethyl)phosphonate

Johnson-Corey-Chaykovsky reaction

epoxidereagent a sulfonium ylide

Oxo Diels Alder reaction

pyran Aldehydes can, typically in the presence of suitable catalysts, serve as partners in cycloaddition reactions. The aldehyde serves as the dienophile component, giving a pyran or related compound.

Hydroacylation ketone In hydroacylation an aldehyde is added over an alkene to form a ketone.

decarbonylation alkane catalysed by transition metals

[edit]Examples of aldehydes

Methanal  (Formaldehyde)

Ethanal  (Acetaldehyde)

Propanal  (Propionaldehyde)

Butanal  (butyraldehyde)

Benzaldehyde

Cinnamaldehyde

Tolualdehyde

[edit]Related compounds

Other kinds of organic compounds containing carbonyl groups include

Dialdehydes

Ketones

Carboxylic acids

Amides

KetoneFrom Wikipedia, the free encyclopedia

Ketone group

Acetone

In organic chemistry, a ketone (pronounced /ˈkiːtoʊn/) is a compound with the structure

RC(=O)R', where R and R' can be a variety of atoms and groups of atoms. It features acarbonyl

group (C=O) bonded to two other carbon atoms.[1] Acetone is the simplest example of a ketone,

and in fact the word ketone derives its name from Aketon, an old German word for acetone.[2]

Ketones differ from aldehydes in that the carbonyl is placed between two carbons rather than at

the end of a carbon skeleton. They are also distinct from other functional groups, such

as carboxylic acids, esters and amides, which have a carbonyl group bonded to a hetero atom.

A ketone that has an α-hydrogen participates in a so-called keto-enol tautomerism. The reaction

with a strong base gives the corresponding enolate, often by deprotonation of the enol.

Contents

 [hide]

1     Nomenclature   

2     Structure and properties   

o 2.1      Classes of ketones   

2.1.1      Diketones   

2.1.2      Unsaturated    

ketones

2.1.3      Cyclic ketones   

o 2.2      Keto-enol tautomerization   

o 2.3      Acidity of ketones   

3     Characterization   

o 3.1      Spectroscopy   

o 3.2      Qualitative organic tests   

4     Synthesis   

5     Reactions   

6     Biochemistry   

7     Applications   

8     Toxicity   

9     See also   

10      References   

[edit]Nomenclature

According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -e of

the parent alkane to -one. For the most important ketones, however, traditional nonsystematic

names are still generally used, for example acetone and benzophenone. These nonsystematic

names are considered retained IUPAC names,[3] although some introductory chemistry

textbooks use names such as 2-propanone or propan-2-one instead of acetone, the simplest

ketone (C H 3-CO-CH3). The position of the carbonyl group is usually denoted by a number.

Oxo is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also

used. For some common chemicals (mainly in biochemistry), "keto" or "oxo" is the term used to

describe the ketonefunctional group. The term "oxo" is used widely through chemistry. For

example, it also refers to a single oxygen atom coordinated to a transition metal (a metal oxo).

[edit]Structure and properties

Representative ketones, from the left: acetone, a common solvent; oxaloacetate, an intermediate in the metabolism

of sugars; acetylacetone in its (mono) enol form (the enol highlighted in blue); cyclohexanone, precursor to

Nylon; muscone, an animal scent; and tetracycline, an antibiotic.

The ketone carbon is often described as "sp2 hybridized," terminology that describes both their

electronic and molecular structure. Ketones are trigonal planar about the ketonic carbon, with C-

C-O and C-C-C bond angles of approximately 120°.

The carbonyl group is polar as a consequence of the fact that the electronegativity of the

oxygen center is greater than that for carbonyl carbon. Thus, ketones are nucleophilic at oxygen

and electrophilic at carbon. Because the carbonyl group interacts with water by hydrogen

bonding, ketones are typically more soluble in water than the related methylene compounds.

Ketones are hydrogen-bond acceptors. Ketones are not usually hydrogen-bond donors and

cannot hydrogen-bond to itself. Because of their inability to serve both as hydrogen-bond

donors and acceptors, ketones tend not to "self-associate" and are more volatile

thanalcohols and carboxylic acids of comparable molecular weights. These factors relate to

pervasiveness of ketones in perfumery and as solvents.

[edit]Classes of ketones

Ketones are classified on the basis of their substituents. One broad classification subdivides

ketones into symmetrical and unsymmetrical derivatives, depending on the equivalency of the

two organic substituents attached to the carbonyl center. Acetone and benzophenone are

symmetrical ketones. Acetophenone (C6H5C(O)CH3) is an unsymmetrical ketone. In the area

of stereochemistry, unsymmetrical ketones are known for being prochiral.

[edit]Diketones

Main article: diketone

Many kinds of diketones are known, some with unusual properties. The simplest

is biacetyl (CH3C(O)C(O)CH3), once used as butter-flavoring in

popcorn. Acetylacetone (pentane-2,4-dione) is virtually a misnomer (inappropriate name)

because this species exists mainly as the monoenol CH3C(O)CH=C(OH)CH3. Its enolate is a

common ligand in coordination chemistry.

[edit]Unsaturated ketones

Ketones containing alkene and alkyne units are often called unsaturated ketones. The most

widely used member of this class of compounds is methyl vinyl ketone, CH3C(O)CH=CH2, which

is useful in Robinson annulation reaction. Lest there be confusion, a ketone itself is a site of

unsaturation; that is, it can be hydrogenated.

[edit]Cyclic ketones

Many ketones are cyclic. The simplest class have the formula (CH2)nCO, where n varies from 3

for cyclopropanone to the teens. Larger derivatives exist. Cyclohexanone, a symmetrical cyclic

ketone, is an important intermediate in the production of nylon. Isophorone, derived from

acetone, is an unsaturated, unsymmetrical ketone that is the precursor to other

polymers. Muscone, 3-methylpentadecanone, is an animalpheromone.

[edit]Keto-enol tautomerization

Main article: Enol

Keto-enol tautomerism. 1 is the keto form; 2 is the enol.

Ketones that have at least one alpha-hydrogen, undergo keto-enol tautomerization; the

tautomer is an enol. Tautomerization may be catalyzed by both acids and bases. Usually, the

keto form is more stable than the enol. This equilibrium allows ketones to be prepared via the

hydration of alkynes.

[edit]Acidity of ketones

Ketones are far more acidic (pKa ≈ 20) than a regular alkane (pKa ≈ 50). This difference reflects

resonance stabilization of the enolate ion that is formed through dissociation. The relative acidity

of the α-hydrogen is important in the enolization reactions of ketones and other carbonyl

compounds. The acidity of the α-hydrogen also allows ketones and other carbonyl compounds

to undergo nucleophilic reactions at that position, with either stoichiometric and catalytic base.

[edit]Characterization

[edit]Spectroscopy

Ketones and aldehydes absorb strongly in infra-red spectrum near 1700 cm −1 . The exact

position of the peak depends on the substituents.

Whereas 1 H NMR  spectroscopy is, in general, not useful for establishing the presence of a

ketone, 13 C NMR  spectra exhibit signals somewhat downfield of 200 ppm depending on

structure. Such signals are typically weak due to the absence of nuclear Overhauser effects.

Since aldehydes resonate at similar chemical shifts, multiple resonance experiments are

employed to definitively distinguish aldehydes and ketones.

[edit]Qualitative organic tests

Ketones give positive results in Brady's test, the reaction with 2,4-dinitrophenylhydrazine to give

the corresponding hydrazone. Ketones may be distinguished from aldehydes by giving a

negative result with Tollens' reagent. Methyl ketones give positive results for the iodoform test.

[edit]Synthesis

Many methods exist for the preparation of ketones in industrial scale, biology, and in academic

laboratories. In industry, the most important method probably involves oxidation of

hydrocarbons, often with air. For example, billion kilograms of cyclohexanone are produced

annually by aerobic oxidation of cyclohexane. Acetone is prepared by air-oxidation of cumene.

For specialized or small scale organic synthetic applications, ketones are often prepared

by oxidation of secondary alcohols:

R2CH(OH) + O → R2C=O + H2O

Typical strong oxidants (source of "O" in the above reaction) include potassium

permanganate or a Cr(VI) compound. Milder conditions make use of the Dess-Martin

periodinane or the Moffatt-Swern methods.

Many other methods have been developed including:

By geminal halide hydrolysis.

By hydration of alkynes. Such processes occur via enols and require the presence of an

acid and HgSO4. Subsequent enol-keto tautomerization gives a ketone. This reaction

always produces a ketone, even with a terminal alkyne.

From Weinreb Amides using stoichiometric organometallic reagents.

Aromatic ketones can be prepared in the Friedel-Crafts acylation, the related Houben-

Hoesch reaction and the Fries rearrangement.

Ozonolysis , and related dihydroxylation/oxidative sequences, cleave alkenes to give

aldehydes and/or ketones, depending on alkene substitution pattern.

In the Kornblum–DeLaMare rearrangement ketones are prepared from peroxides and

base.

In the Ruzicka cyclization, cyclic ketones are prepared from dicarboxylic acids.

In the Nef reaction, ketones form by hydrolysis of salts of secondary nitro compounds.

In the Fukuyama coupling, ketones form from a thioester and an organozinc compound.

By the reaction of an acid chloride with organocadmium compounds or organocopper

compounds.

The Dakin-West reaction provides an efficient method for preparation of certain methyl

ketones from carboxylic acids.

Ketones can also be prepared by the reaction of Grignard reagents with nitriles, followed

by hydrolysis.

By decarboxylation of carboxylic anhydride.

Ketones can be prepared from haloketones in reductive dehalogenation of halo ketones.

[edit]Reactions

Ketones engage in many organic reactions. The most important reactions follow from the

susceptibility of the carbonyl carbon toward nucleophilic addition and the tendency for the

enolates to add to electrophiles. Nucleophilic additions include in approximate order of their

generality:

With water (hydration) gives geminal diols, which are usually not formed in appreciable

(or observable) amounts

With an acetylide to give the α-hydroxyalkyne

With ammonia or a primary amine gives an imine

With secondary amine gives an enamine

With Grignard and organolithium reagents to give, after aqueous workup, a tertiary

alcohol

With an alcohols or alkoxides to gives the hemiketal or its conjugate base. With a diol to

the ketal. This reaction is employed to protect ketones.

With sodium amide resulting in C-C bond cleavage with formation of the amide

RCONH2 and the alkane R'H, a reaction called the Haller-Bauer reaction.[4]

Electrophilic addition , reaction with an electrophile gives a resonance stabilized cation

With phosphonium ylides in the Wittig reaction to give the alkenes

With thiols to give the thioacetal

With hydrazine or 1-disubstituted derivatives of hydrazine to give hydrazones.

With a metal hydride gives a metal alkoxide salt, hydrolysis of which gives the alcohol,

an example of ketone reduction

With halogens to form α-haloketone, a reaction that proceeds via an enol (see Haloform

reaction)

With heavy water to give a α-deuterated ketone

Fragmentation in photochemical Norrish reaction

Reaction of 1,4-aminodiketones to oxazoles by dehydration in the Robinson-Gabriel

synthesis

In the case of aryl-alkyl ketones, with sulfur and an amine give amides in the Willgerodt

reaction

With hydroxylamine to produce oximes

[edit]Biochemistry

Acetone, acetoacetate, and beta-hydroxybutyrate are ketones (or ketone bodies)

generated from carbohydrates, fatty acids, and amino acids in humans and

most vertebrates. Ketones are elevated in blood after fasting including a night of sleep, and

in both blood and urine in starvation, hypoglycemia due to causes other

than hyperinsulinism, various inborn errors of metabolism, and ketoacidosis (usually due

to diabetes mellitus). Although ketoacidosis is characteristic of decompensated or

untreated type 1 diabetes, ketosis or even ketoacidosis can occur in type 2 diabetes in

some circumstances as well. Acetoacetate and beta-hydroxybutyrate are an important fuel

for many tissues, especially during fasting and starvation. The brain, in particular, relies

heavily on ketone bodies as a substrate for lipid synthesis and for energy during times of

reduced food intake. Ketones have been described as "magic" in their ability to increase

metabolic efficiency, while decreasing production of free radicals, the damaging byproducts

of normal metabolism. Ketone bodies are relevant to neurological diseases such as

Alzheimer's and Parkinson's disease,[5] and the heart and brain operate 25% more

efficiently using ketones as a source of energy.[6] Research has also shown ketones play a

role in reducing epileptic seizures with the high-fat, near-zero carbohydrate Ketogenic

Diet. [1]

[edit]Applications

Ketones are produced on massive scales in industry as solvents, polymer precursors, and

pharmaceuticals. In terms of scale, the most important ketones are acetone, methylethyl

ketone, and cyclohexanone. They are also common in biochemistry, but less so than in

organic chemistry in general. The combustion of hydrocarbons is an uncontrolled oxidation

process that gives ketones as well as many other types of compounds.

[edit]Toxicity

Although it is difficult to generalize on the toxicity of such a broad class of compounds,

simple ketones are, in general, not highly toxic (for instance, the sugar fructose is a

ketone). This characteristic is one reason for their popularity as solvents. Exceptions to this

rule are the unsaturated ketones such as methyl vinyl ketone with LD50 of 7 mg/kg (oral).

Ketone bodiesFrom Wikipedia, the free encyclopedia

Chemical structures of the three ketone bodies: acetone (top),acetoacetic acid(middle), and beta-hydroxybutyric

acid(bottom).

Ketone bodies are three water-soluble compounds that are produced as by-

products when fatty acids are broken down for energy in the liver and kidney. They are used as

a source of energy in the heart and brain. In the brain, they are a vital source of energy

during fasting.[1] Although termed "bodies", they are dissolved substances, not particles.

The three endogenous ketone bodies are acetone, acetoacetic acid, and beta-hydroxybutyric

acid,[2] although beta-hydroxybutyric acid is not technically a ketone but a carboxylic acid. Other

ketone bodies such as beta-ketopentanoate and beta-hydroxypentanoate may be created as a

result of the metabolism of synthetic triglycerides such as triheptanoin.

Contents

 [hide]

1     Uses in the heart and brain   

2     Production   

3     Ketosis and ketoacidosis   

4     Impact upon pH   

5     See also   

6     References   

7     External links   

Uses in the heart and brain

Ketone bodies can be used for energy. Ketone bodies are transported from the liver to other

tissues, where acetoacetate and beta-hydroxybutyrate can be reconverted to acetyl-CoA to

produce energy, via the citric acid cycle.

The heart gets little energy from ketone bodies except under special circumstances; it uses

mainly fatty acids.[3][4]

The brain gets its energy from ketone bodies when glucose is less available (e.g., when fasting).

In the event of low blood glucose, most other tissues have additional energy sources besides

ketone bodies (such as fatty acids), but the brain does not. After the diet has been changed to

lower blood glucose for 3 days, the brain gets 30% of its energy from ketone bodies.[5] After

about 40 days, this goes up to 70% (during the initial stages the brain does not burn ketones,

since they are an important substrate for lipid synthesis in the brain). In time the brain reduces

its glucose requirements from 120g to 40g per day.[6][unreliable source?]

Production

Acetyl-CoA

Ketone bodies are produced from acetyl-CoA (see ketogenesis) mainly in

the mitochondrial matrix of hepatocytes when carbohydrates are so scarce that energy must be

obtained from breaking down fatty acids. Because of the high level of acetyl CoA present in the

cell, the pyruvate dehydrogenase complex is inhibited, whereas pyruvate carboxylase becomes

activated. Thus, the oxaloacetate produced will enter gluconeogenesis rather than the citric acid

cycle, as the latter is also inhibited by the elevated level of NADH resulting from ß-oxidation of

fatty acids. The excess acetyl-CoA is therefore rerouted to ketogenesis. Such a state in humans

is referred to as the fasted state.

Acetone is produced by spontaneous decarboxylation of acetoacetate, yielding levels of

acetone much lower than those of other ketone bodies. Acetone cannot be converted back to

acetyl-CoA; it is instead metabolized (e.g., converted to glucose via pyruvate[7]), excreted in

the urine, or (as a consequence of its high vapor pressure) exhaled. Acetone is responsible for

the characteristic "fruity" odor of the breath of persons in ketoacidosis.[8]

Ketosis and ketoacidosis

Any production of these compounds is called ketogenesis, and this is necessary in small

amounts.

However, when excess ketone bodies accumulate, this abnormal (but not necessarily harmful)

state is called ketosis. Ketosis can be quantified by sampling the patient's exhaled air, and

testing for acetone by gas chromatography.[9] Many diabetics self test for the presence of

ketones using blood or urine testing kits.

When even larger amounts of ketone bodies accumulate such that the blood's pH is lowered to

dangerously acidic levels, this state is called ketoacidosis.

Impact upon pH

Both acetoacetic acid and beta-hydroxybutyric acid are acidic, and, if levels of these ketone

bodies are too high, the pH of the blood drops, resulting in ketoacidosis.

This happens in untreated Type I diabetes (see diabetic ketoacidosis), and also

in alcoholics after binge drinking, subsequent to starvation, and as a result of the alcohol-

induced impairment of the liver's ability to generate glucose by the process

of gluconeogenesis (see alcoholic ketoacidosis).

Posted by Christopher in Facts - (0 Comments)

Ketones are an ordinary and proficient cause of stimulation and powerful energy for the human body. They are formed by the liver as of the fat as it is given out from fat cells in retort to the nonexistence of glucose or the so called sugar in the diet.  Our body functions all the time unlike the human. So obviously it needs more energy which is produced by the liver. When the human body is producing ketones, and using them for producing energy, it is termed as “ketosis”.Ketosis is usual and not hazardous. The body produces ketones to use as energy at the time when there is absence of sugar. The major fact to remember is that, ketones can be created by fat we consume, so it is necessary to minimize the fat intake and also the sugar as when the sugar level raises it causes ketone problem. As a consequence the resulting factor in the human body is required to generate and utilize ketones for all the body activities.Ketones are to take care in a proper way as taking proper medication for the disease would be life saving. They are very important as they are responsible for the energy generation for our body to enhance the metabolism .If it fails the metabolic activities are in trouble which leads gradually to death. Proper medication has to be given to any diabetic patient as it would start to affect the body parts one by one causing dehydration.

Posted by Christopher in Facts - (0 Comments)

The most common induce of ketosis is constantly dieting. Individuals who go on sudden low-carb dieting

often complain of weight loss, accompanied along ketosis symptoms. One of the main symptoms of

ketosis is while a person shifts from highly glycemic dieting to a dieting which doesn’t provide enough

glycogen stores. This happens when the body gets into a level of ketosis. In the starting stage, the brain

doesn’t burn ketones, just even after 2 days also if carbohydrates aren’t included in your diet, then the

brain begins burning ketones hence it directly uses the vitality from its adipose tissue stores, hence,

preserving glucose just for dreadful conditions, and precluding collapse of the body’s muscle and protein.

Although still problematical, this level of ketosis is regarded as relatively safe. In fact, in some cases

ketosis is deliberately caused in the ketogenic dieting, which is utilized to treat epilepsy. Still, prolonged

ketosis is capable of causing the body and also it is highly discouraged. Sustained ketosis symptoms are

much seen in individuals that move to fad dieting for weight loss.

You should learn to point the symptoms of ketosis before it grows into DKA. As there is excessively little

insulin, the level of blood sugar will normally be high. You may also be experiencing either one or more

like urinating more frequently, being sick or feeling sick, finding it difficult to breathe, breathe that odor of

pear drops, feeling thirsty for all the time, flushed skin or having dry, feeling tired or confused, pain in your

abdomen.

Posted by Christopher in Facts - (0 Comments)

Ketones formation:

Ketones are formed when our human body gets power by flouting down fat as an alternative of sugar. The

major reason for this alternative breaking is that there is no enough insulin in the blood and not enough

sugar is available.

Ketones in severe stage:

Ketones become a difficulty when the patient does not have an adequate amount of insulin to organize

ketone creation correctly or they are ravenous because of lack of food. When more amounts of ketones

are formed too swiftly they disturb the fragile equilibrium of the body’s metabolism and can direct to a

crisis called diabetic ketoacidosis.

Who is vulnerable to Ketones?

Populace, who make use of insulin at the time of sickness, and now and then anxiety, can make ketone

levels increase. Children who suffer with diabetes every so often can face the trouble to let know the

symptoms of growing ketones as of additional early day’s sickness. Pregnant women with diabetes may

have far above the ground ketone levels can have an effect on the baby inside, so expectant women with

diabetes required to take additional concern.

How to identify the signs of ketones:

Because there is too small insulin, blood sugar levels will typically be elevated. There are many

symptoms experienced by the patients.

Urinating more recurrently

Having dehydrated skin

sensation unwell or being unwell

Feeling weary and perplexed

Finding tough to respire

Chronic pain in  stomach

Prevailing of thirsty always.

Some of these symptoms occur because as ketone stage rises, blood becomes further acidic. This

causes the Acidic blood, joint with lack of moisture resulting in dehydration, cause diabetic ketoacidosis

Posted by Christopher in Facts - (0 Comments)

Ketone bodies are 3 water-soluble compounds which are developed as by-products while fatty acids are

collapsed for energy in the kidney and  liver. They are utilized as a source of vitality in the brain and heart.

Brain, is the vital source of energy during fasting. Though it is termed as “bodies”, they are broke up

substances, not particles. The 3 endogenous ketone bodies are acetoacetic acid, acetone,  and beta-

hydroxybutyric acid, though beta-hydroxybutyric acid isn’t actually a ketone simply a carboxylic acid.

Remaining ketone bodies like beta-hydroxypentanoate  and beta-ketopentanoate   may be developed as

an outcome of metabolism of celluloid triglycerides like triheptanoin.

Ketone bodies can also be utilized for vitality. Ketone bodies are carried from liver to other tissues, at

which beta-hydroxybutyrate and acetoacetate  can be again converted to acetyl-CoA to acquire energy,

through citric acid cycle. The heart acquires little vitality from ketone bodies excluding under peculiar

circumstances; it utilizes mainly fatty acids.

The brain acquires its vitality from ketone bodies while glucose is available in less number. e.g.,

when fasting. In the case when the blood glucose level is low, most other tissues induce additional vitality

sources as well ketone bodies like fatty acids, only the brain doesn’t.  After the diet the level of blood

glucose will be lowered and it will be for 3 days, the brain acquires 30% of its vitality from ketone

bodies. Later on about forty days, this rises up to 70% i.e. during the starting stages the brain doesn’t

burn ketones, as for lipid deductions in the brain they are considered as an important substrate.

Posted by Christopher in Facts - (0 Comments)

Ketone (ketone body): in the liver, fatty acid oxidation and decomposition of the intermediate product

acetoacetate, β-hydroxybutyric acid and acetone, the three collectively known as ketone bodies.

Liver synthesis of ketone bodies with strong enzymes, but the lack of the enzyme by ketone bodies.

Ketone is a product of lipolysis, rather than a product of high blood sugar. Eating carbohydrates will not

lead to an increase in ketone bodies.

During starvation Ketone bodies provide a source of power for many parts of the body, including the

brain, and therefore have important physiological significance.

The importance of ketone bodies is that, due to the presence of blood-brain barrier, in addition to glucose

and ketone body substances outside the brain cannot enter the brain to provide energy.

 

During starvation ketone provides 25% -75% enegry to our brain. However, too much ketones cause

poisoning. Avoid excessive ketone body production, the must be a good supply of sugar.

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