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Copyright © Houghton Mifflin Company. All rights reserved. 3–1
13 Hydrocarbon Derivatives II
Compounds with carbon-oxygen double bonds
Aldehydes
KetonesCarboxylic Acids
Esters
Amides
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13 Hydrocarbon Derivatives II
The carbon-oxygen double bond is called a carbonyl group, and occurs in different functional groups.
R1C
O
R2
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13 Hydrocarbon Derivatives II
The carbon of the carbonyl group has trigonal planar electronic and molecular geometry.
The carbonyl group is polar.
R1C
O
R2
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13.2 Naming AldehydesAldehydes have at least one hydrogen
substituent on the carbonyl group. The other substituent can be any hydrocarbon.
HC
H
O
H3CC
H
O
CO
HN
H3C
H3C
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13.2 Naming Aldehydes
Suffix is “-al”
1. Find longest chain that bears carbonyl
2. Number carbon chain so carbonyl is #1
3. Locate and name any other substituents
4. Final “e” on name of hydrocarbon is dropped
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13.2 Naming Aldehydes
Common names are frequently used too.
HC
H3C
O
HC
H
O
IUPAC methanal ethanal propanal
Common formaldehyde acetaldehyde propionaldehyde
H3C CH2C
O
H
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13.2 Naming Aldehydes
Aromatic aldehydes are named as benzaldehydes.
CH
O
Benzaldehyde
CH
O
Cl
Cl
2,4-dichlorobenzaldehyde
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13.4 Naming Ketones
Ketones have two hydrocarbon substit-uents on the carbonyl group. The carbonyl group can be in a ring.
H3CC
CH3
OC
O
C
O
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13.4 Naming Ketones
Suffix is “-one”
1. Find longest chain that bears carbonyl
2. Number carbon chain so carbon bearing C=O has lowest possible number; it cannot be #1
3. Locate and name any other substituents
4. Final “e” on name of hydrocarbon is dropped
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13.4 Naming KetonesCommon names are frequently used.
They are formed by naming the alkyl substituents on the carbonyl, usually in alphabetical order.
IUPAC
Common
H3CC
CH3
O
H3CC
CH2
O
CH3
2-propanone 2-butanone
acetone methyl ethyl ketone (MEK)
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13.4 Naming Ketones
Compounds with carbonyl groups in rings are named as cycloalkanones. The carbonyl carbon is #1; this locant is understood and not given.
C
O
C
OCH3
CH3
Cl
cyclohexanone 4-chloro-2,2-dimethylcyclopentanone
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13.4 Naming Ketones
Aromatic ketones are named as phenones, or as ketones with phenyl and alkyl substituents.
C
O
CCH3
O
benzophenone acetophenone
diphenyl ketone methyl phenyl ketone
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13.4 Naming Ketones
Acetyl groups are carbonyl groups bonded to methyl groups. “Acet-” and “aceto-” appear often in names of carbonyl compounds.
H3CC
O
acetylgroup
H3CC
H
O
acetaldehyde
H3CC
CH3
O
acetone
H3CC
OH
O
aceticacid
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13.3,5 Properties of Aldehydes and Ketones
Aldehydes and ketones have similar prop-erties and undergo similar reactions. These will be considered together.
Aldehydes and ketones are polar, but are not hydrogen bond donors. Their boiling points are intermediate between alcohols and alkanes/ethers.
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13.3,5 Properties of Aldehydes and Ketones
Aldehydes and ketones have similar prop-erties and undergo similar reactions. These will be considered together.
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13.3,5 Properties
Aldehydes and ketones can act as hydrogen bond acceptors. Small compounds are appreciably soluble in water.
Formaldehyde, acetaldehyde, and acetone are completely soluble in water.
C O H OH
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13.3,5 Reactions
Aldehydes are generally more reactive than ketones, and can undergo some reactions that ketones do not. There are more sim-ilarities than differences.
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13.3,5 Reactions
Aldehydes are easily oxidized to carboxylic acids.
Ketones are not easily oxidized.
C
O
H O2C
O
OH
benzaldehyde,viscous liquid,
almond fragrance
benzoic acid,white solid,
no fragrance
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13.3,5 Reactions
Tollens’ test is an oxidation of aldehydes by Ag1+, which is reduced to silver metal.
RC
H
O+ Ag1+ NH3
H2O RC
OH
O+ Ag(metal)
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13.3,5 Reactions
Aldehydes and ketones can be reduced to alcohols.
RC
H
O[H2]
OH
CHR
H 1° alcohol
R1CR2
O[H2]
OH
CR2R1
H 2° alcohol
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13.3,5 Reactions
Catalytic hydrogenation works, but more often NaBH4 or LiAlH4 is used. These compounds behave as sources of hydride anion, H1–.
B
H
H
H
HNa Al
H
H
H
HLi
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13.3,5 ReactionsHydration is addition of water across the
C=O bond. It is similar to addition across a C=C bond.
Aldehydes hydrate more readily than ketones. Formaldehyde hydrates completely. Formalin is a solution of hydrated formaldehyde.
R1 CO
H+ H2O R1 C
H
OH
OH
hydrated aldehyde
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13.3,5 Reactions
Alcohols can add across a C=O bond. The product is called a hemiacetal.
Ketones undergo the same reaction, but less readily. The product is sometimes called a hemiketal. We’ll call both types hemiacetals.
R1 CO
H+ HO R2 R1 C
H
OH
O R2
hemiacetal
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13.3,5 Reactions
Hemiacetals have ether and hydroxyl groups on the same carbon.
The two structures are in equilibrium, and the hemiacetal can be difficult to isolate.
R1C
R2
O+ R3OH
O
CR2R1
O
R3
HR2 can be H
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13.3,5 Reactions
Carbonyl compounds with hydroxyl groups three or four carbons away readily form cyclic hemiacetals.
R1C
CH2
O
CH2 CH2 O HO
OHR1
R1C
CH2
O
CH2 CH2 CH2 OO
H
OHR1
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13.3,5 ReactionsIn the presence of excess alcohol, acetals
form. Acetals of ketones may be called ketals.
The equilibrium is not favorable for the reac-tion. Catalysis speeds it up, and water removal drive it to completion.
R1C
R2
O+ 2 R3OH
O
CR2R1
O
R3
R3
R2 can be H
H3O1+ catalyst+ H2O
heat− H2O
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13.3,5 Reactions
Acetals have two ether groups on the same carbon. Like ethers, they are not very reactive.
O
CR2R1
O
R3
R3
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13.3,5 Reactions
Acetals can be converted back to the parent aldehydes or ketones with water and an acid catalyst.
O
CR2R1
O
R3
R3
+ H2OH3O1+ catalyst
R1C
R2
O+ 2 R3OH
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13.3,5 Reactions
Diols give cyclic acetals.
C
O
+ HO CH2 CH2 OHheat− H2O
H3O1+ OO
ethylene glycol
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Common AldehydesFormaldehyde, the simplest aldehyde, is used
for sterilizing apparatus and as an embalm-ing fluid.
It is also a component of synthetic resins, e.g. phenol-formaldehyde (Bakelite), and melamine-formaldehyde (Formica).
HC
H
O
formaldehyde
+ H2OH
CH
OHHO
formalin
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Common AldehydesAldehydes are components of flavors and odors.
CO
H
benzaldehyde,almond oil
CO
HHO
OH3Cvanillin
CC
C
O
H
H
H
CO
HCH
H3C
H3C
cinnamaldehyde cuminaldehyde
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Common Ketones
Simple ketones are solvents and degreasers.
Simple aldehydes are too reactive and toxic to be used as solvents.
H3CC
CH3
O
H3CC
CH2
O
CH3
acetone methyl ethyl ketone (MEK)
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Common Ketones
Aromatic ketones are used as photoinitiators for resin that cure in ultraviolet light, such as those in dental sealants.
C
O
benzophenone
C
OOH
hydroxycyclohexyl-phenyl ketone
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Common Ketones
Ketones are functional groups in some steroid hormones.
O
O OH
O
cortosone
OH
O
O
progesterone
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13.6 Carboxylic Acids
Carboxylic acids have a carboxyl group (COOH) on a hydrocarbon chain; R–COOH
The carboxyl group has a hydroxyl group on a carbonyl carbon.
RC
OH
O
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13.6 Naming Carboxylic Acids
Suffix is “-oic acid”
1. Find longest chain that bears –COOH
2. Number carbon chain so –COOH is #1
3. Locate and name any other substituents
4. Final “e” on name of hydrocarbon is dropped
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13.6 Naming Carboxylic AcidsSimple carboxylic acids are often known by
common names.
OHC
H3C
O
HC
OH
O
IUPAC methanoic acid ethanoic acid
butanoic acid
Common formic acid acetic acid
butyric acid
H3C CH2 CH2C
O
OH
IUPAC
Common
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13.6 Naming Carboxylic Acids
Aromatic carboxylic acids are named as derivatives of benzoic acid.
C
O
OHC
O
OH
benzoic acid
OH
2-hydroxybenzoic acida.k.a. salicylic acid
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13.6 Naming Carboxylic Acids
Aromatic dicarboxylic acids are named as phthalic acids, because the ortho isomer was originally made from naphthalene.
C
O
OH
C
O
OH
phthalic acid,ortho-phthalic acid
C
O
HOC
O
OH
isophthalic acid,meta-phthalic acid
C
O
OH
C
O
HO
terephthalic acid,para-phthalic acid
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13.7 Properties of Carboxylic Acids
Carboxylic acids with up to nine carbon atoms are liquids with pungent odors.
Acetic acid, in vinegar, is a good example. “Acet” comes from “vinum acetum,” sour wine.
Larger molecules are waxy solids, as are aromatic carboxylic acids.
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13.7 Properties of Carboxylic Acids
Carboxylic acids with up to nine carbon atoms are liquids with pungent odors.
H3C-CH2-CH2 CO
OH
H3C CO
OH
H3C-(CH2)4 CO
OH
Acetic acid
Butyric acid
Caproic acid
Vinegar
Rancid butter
Goat cheese
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13.7 Properties of Carboxylic AcidsCarboxylic acids are polar, and form dimers
through hydrogen bonding. They have have quite high melting and boiling points.
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13.7 Properties Carboxylic
Acids
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13.7 Properties of Carboxylic Acids
Carboxylic acids are slightly more sol-uble in water than alcohols with the same number of carbons.
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13.7 Acidity of Carboxylic Acids
Carboxylic acids are proton donors.
When R is alkyl, Keq is about 10–5.
Keq = [H3O1+][RCOO1–]
[RCOOH][H2O]
Less than 5% of the molecules are ionized.
R CO
O+ R C
O
OH
OHH
OHH
+H
Carboxylateanion
Hydroniumcation
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13.7 Acidity of Carboxylic Acids
In organic chemistry, we often show ionic charges on specific atoms. These are called “formal charges.”
CH3 CO
OO
HH
H
Acetateanion
Hydroniumcation
OHH
H
1+
CH3 CO
O
1−
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13.7 Acidity of Carboxylic Acids
In strong base, ionization is complete.
Carboxylate anions are stabilized by resonance.
R CO
O+ R C
O
OHO +
Carboxylateanion
H
Hydroxideanion
OHH
R CO
OR C
O
O
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13.7 Acidity of Carboxylic Acids
In strong acid, the carboxylate is completely protonated.
+ OHH
R CO
O
OHH
+H
R CO
O H
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13.7 Naming Carboxylate Salts
Carboxylate anions are named as the “-ate” anion of the conjugate acid.
CH3 CO
O
acetate
CH3 CH2 CH2 CO
OC
O
O
butanoate(butyrate)
benzoate
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13.7 Naming Carboxylate Salts
Ionic compounds are also called “salts.” Those that contain carboxylate anions are named with the cation (usually a metal) followed by the name of the carboxylate.
C
C
O
O
O
OCu2+CH3 C
O
ONa C
O
OK1+
Sodium acetate Potassium benzoate Copper (II) phthalate
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13.7 Reactions of Carboxylic AcidsAcid-base reactions:
Carboxylic acids equilibrate with their conjugate bases in water.
RCOOH + H2O RCOO1– + H3O1+
Carboxylic acids deprotonate to carboxylate salts in strong bases.
RCOOH + OH1– RCOO1– + H2O
Carboxylate anions are protonated in strong acids.
RCOO1– + H3O1+ RCOOH + H2O
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13.7 Reactions of Carboxylic AcidsCondensation reactions:
Condensation reactions are reactions in which two molecules combine into one, with the expulsion of a small molecule such as water.
The dehydration of alcohols to form ethers is a condensation reaction.
R CH2 O H + H O CH2 RH2SO4
140° C
R CH2 O CH2 R + H2O
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13.7 Reactions of Carboxylic Acids
Esters are produced by the condensation of a carboxylic acid and an alcohol.
Keq is often near 1. In the classic Fischer Esterification, H2SO4 is the catalyst.
CO
OH+ HO CH3 C
O
O CH3
+ H2OH1+
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13.7 Reactions of Carboxylic Acids
Lactones are cyclic esters. They are formed by intramolecular conden-sations of hydroxy acids.
HO CH2 CH2 CH2 CO
OH
catalyst
OC O + H2O
γ-butyrolactone
HO CH2 CH2 CH2 CH2 CO
OH
catalyst+ H2O
δ-valerolactoneOC O
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13.7 Reactions of Carboxylic Acids
Amides are produced by the condensation of a carboxylic acid and ammonia or an amine.
The amine must have at least one hydrogen, or water cannot form.
CO
OH+ C
O
N CH3
+ H2OH1+
HNCH3
CH3
CH3
heat
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13.7 Reactions of Carboxylic Acids
Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants.
“Heat” means > 200C (>400F) to decompose the salt and form the amide.
mild
conditionsC
O
O+
HC
O
ON
CH3
HCH3
+ NCH3
HCH3
H
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Important Carboxylic Acids
Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants.
“Heat” means > 200C (>400F) to decompose the salt and form the amide.
H3C CO
OH
H CO
OH
Formic acid, simplest carboxylicacid, used in antimicrobials andleather tanning
Acetic acid, the most commoncarboxylic acid, found in vinegarand widely used in industry.
C CO
OH
H
CHH
C CO
OH
H3C
CHH
Acrylic acid, simplest unsaturatedcarboxylic acid, used to makewater-soluble polymers
Methacrylic acid, used to makeesters and polymeric derivatives
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Important Carboxylic Acids
Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants.
“Heat” means > 200C (>400F) to decompose the salt and form the amide.
CO
OH
C
C
O
OH
O
OH
CO
HO
O
OH
Benzoic acid, simplest aromaticcarboxylic acid, used as a foodpreservative and industrial feed.
o-Phthalic acid, generally usedas its anhydride, in plasticisersand dyes
Terephthalic acid, used in polyester plastics and fibers
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Important Carboxylic Acids
Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants.
“Heat” means > 200C (>400F) to decompose the salt and form the amide.
CH3 CH
OH
CO
OH
Lactic acid, "milk acid," is importantin metabolism in its anionic form
CH3 C
O
CO
OH
Pyruvic acid is a metabolite of glucosethat enters the Citric Acid Cycle. The name comes from "pyrolysis of grapes."
Salicylic acid, "willow acid," is anantiinflammatory and antipyretic; esters are aspirin and wintergreen
C
O
OH
OH
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Important Carboxylic Acids
Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants.
“Heat” means > 200C (>400F) to decompose the salt and form the amide.
C
O
OH
Stearic acid, "typical" saturated fatty acid
Oleic acid, from olives, monounsaturated fatty acid
O
OH
Linoleic acid, from vegetable oils, polyunsaturatedfatty acid. Essential in diet; used in oil paints
O
OH
Linolenic acid, from vegetable oils, polyunsaturatedfatty acid. Essential in diet; used in oil paints
O
OH
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13.8 Esters
Esters are derivatives of carboxylic acids.
They have an alkoxy group (–OR) on a carbonyl carbon.
R1C
O
OR2
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13.8 Naming Esters
Esters are condensation products of alcohols and carboxylic acids. They are named as alkyl alkanoates. The alkyl group is de-rived from the alcohol; the alkanoate is de-rived from the acid. The -oic acid suffix or the acid is replaced by -ate.
CO
OH+ HO CH3 C
O
O CH3
+ H2OH1+
Benzoic acid Methanol Methyl benzoate
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13.8 Naming Esters
Esters are condensation products of alcohols and carboxylic acids. They are named as alkyl alkanoates. The alkyl group is de-rived from the alcohol; the alkanoate is de-rived from the acid. The -oic acid suffix or the acid is replaced by -ate.
CH3 C
O
OH + H2O CH2 CH3 CH3 C
O
O CH2 CH3 + H2O
Ethanoicacid, a.k.a.Acetic acid
Ethanol Ethyl ethanoate, a.k.a.Ethyl acetate
+ HO CH3 + H2O
Methanol
CH3 CH2 C
O
OH
Propanoic acid
CH3 CH2 C
O
O CH3
Methyl propanoate
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13.9 Properties of Esters
Esters are polar, but cannot form hydrogen bonds. They are slightly soluble in water. Boiling points are somewhat lower than those of structurally similar ketones.
CH3−CH−CH2−CH3
CH3
CH3−CH−CH2−CH3
OH
CH3−C−CH2−CH3
O
CH3−C−O−CH3
O
bp = 28oC bp = 57oC bp = 80oC bp = 99oC
OO
O
bp = 218oCbp = 199oC
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13.9 Properties of Esters
Most simple esters are liquids. Many have fruity or floral fragrances.
H3CC
O
O
CH2 CH2 CH
CH3
CH3
Isoamyl acetateBanana scent
C
O
OCH3
OH
Methyl salicylateWintergreen scent
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13.9 Reactions of EstersHydrolysis:
The main reaction of esters is hydrolysis (breaking with water). It is the reverse of the condensation reaction.
Like formation of the ester, Keq is ~1. Excess water increases the amount of hydrolyzed product.
CO
OH+ HO CH3C
O
O CH3
+ H2OH1+
Benzoic acid MethanolMethyl benzoate
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13.9 Reactions of Esters
Hydrolysis of esters in base is called saponification, a.k.a. soap-making!
One uses at least an equivalent of OH1–, and the acid is isolated as its carbox-ylate salt. Formation of the salt drives the reaction to completion.
CO
O+ HO CH3C
O
O CH3
+ NaOHH2O
Sodiumbenzoate
Methanol
+ Na
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13.9 Reactions of Esters
Transesterification:It is often easier to prepare complex esters or amides from simple esters than from the acids.
C CO
O
H3C
CHH
2 + HO CH2 CH2 OHSnO(C4H9)2
C CO
O
H3C
CHH
CCO
O
CH3
C HH
CH2 CH2
+ 2 CH3OH
Ethylene glycol dimethacrylate
CH3
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13.9 Reactions of EstersTransesterification:
It is often easier to prepare complex esters or amides from simple esters than from the acids.
CH3(CH2)16 CO
O CH3
2
methyl stearate
+ H2N CH2 CH2 NH2heat
CH3(CH2)16 CO
N CH2
ethylene diamine
HCH2 N
H
CO
(CH2)16CH3 + 2 CH3OH
ethylene bis stearamide
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Important Esters
Transesterification:It is often easier to prepare complex esters or amides from simple esters than from the acids.
H3C CO
O CH2 CH3
Ethyl acetate, industrial solvent, found in nail polish remover
CHOO
O CO
CH3
Acetylsalicylic acid, Aspirin, acetateester of salicylic acid; antiinflammatoryand antipyretic, not as irritating to thestomach as salicylic acid
C
O
O
OH
CH3 Methyl salicylate, rubifacient (causesreddening of skin by dilating capillaries)for topical pain relief; oil of wintergreen
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Important Esters
Transesterification:It is often easier to prepare complex esters or amides from simple esters than from the acids.
CH O
CH2 O
CH2 O
C
O
R2
C
O
R1
C
O
R3
Triglyceride esters,important lipids
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13.10 Amides
Amides are derivatives of carboxylic acids.
They have an amine group on a carbonyl carbon. Any of the R’s can be H.
R1C
O
NR2
R3
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13.10 Amides
Amines are classified by the number of carbon atoms bonded to the nitrogen atom.
Primary (1°) Secondary (2°) Tertiary (3°)
R1C
O
N
H
HR1
C
O
N
H
R2 R1C
O
N
R3
R2
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13.10 Naming Amides
Suffix is “amide”
1. Root is derived from carboxylic acid
2. IUPAC names for secondary and tertiary amides involve use of the prefix “N-” for the amine substituents. If the same group appears twice, use “di-” and prefix.
3. IUPAC names for amides of simple acids allow the acid’s common name to be used.
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13.10 Naming Amides
Suffix is “amide”
1. Root is derived from carboxylic acidH
CNH2
O
Methanamide,Formamide
H3CC
N
O
CH2 CH3
H
N-ethylethanamide,N-ethylacetamide
C
O
NCH3
CH3
N,N-dimethyl-benzamide
CH3 CH2 CO
NH
2-methylbutanamide
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13.10 Naming Amides
Compounds in which a carbonyl group is flanked by two nitrogen atoms are called ureas.
N
NN
NOON
CN
O
H
H
H
H
H
H H
H
Urea Glycouril
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13.10 Naming Amides
Compounds in which carbonyl groups appear on either side of the nitrogen are called imides. Cyclic imides are more common than straight-chain molecules.
CN
C
O
O
H
Phthalimide
CN
C
O
O
Br
N-bromosuccinimide,NBS (Br2 source)
CN
C
O
O
CH2 CH3
N-ethylmaleimide,NEM, used in enzyme
research
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13.11 Properties of Amides
Amides have resonance structures that cause the nitrogen atom to be trigonal planar, sp2.
Rotation about the CN bond is restricted.
R1C
O
N
H
R2 R1C
O
N
H
R2
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13.11 Properties of Amides1 and 2 amides have
strong dipoles and hydrogen bonds.
For 2 amides, the fa-vored conformation has the H atom op-posite the O atom. The dipole-dipole forces and hydro-gen bonds are quite strong.
R1C
O
N
H
R2
R1C
O
N
H
R2
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13.11 Properties of Amides1 and 2 amides have the highest melting and
boiling points of common compounds. 3 amides are usually high-boiling liquids.
RC
OH
O
RC
N
O
H
H
RC
N
O
CH3
H
RC
N
O
CH3
CH3
101° 8°
210° 3°
199° −3°
153°−61°
BPMP
119° 17°
222° 81°
206° 28°
166°−20°
BPMP
BPMP
249°123°
N/A128°
N/A 78°
N/A 45°
R = H
R = CH3
R = C6H5
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13.11 Properties of AmidesAll amides are hydrogen-bond acceptors.
Those with fewer than 6 carbons are freely soluble with water.
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13.11 Reactions of Amides
Hydrolysis:The main reaction of amides is hydrolysis. The reaction always requires acid or base.
R1C
O
N
R3
R2 + H2OR1
C
O HN
R3
R2
OH+
slow,Keq << 1
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13.11 Reactions of Amides
Formation of the ammonium cation in acid or the carboxylate anion in base drives the equilibrium to the right.
R1C
O
N
R3
R2 + H3O1+ + H2OR1
C
ON
R3
R2
OH+
H
H
R1C
O
N
R3
R2 + OH1− + H2OR1
C
O
O+
HN
R3
R2
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Important AmidesSimple amides: various small molecules
HC
N
O
CH3
CH3
Dimethyl formamide, DMFhigh-boiling polar solvent
NC
O
CH3
N-methylpyrrolidone, NMP,high-boiling polar solvent
NC
N
O
H
H
H
H
Urea, metabolite of aminoacids, fertilizer
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Important Amides-lactam antibiotics:
Penicillins, cephalosporins, and related antibiotics contain the -lactam group.
R2
OHO
N
NR1
O
O
HS
C N
S CH3
CH3
CO
OH
HH
NC
H
O
R
Cephalosporin
O
Penicillin
C NO H
-lactam
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Important Amides
Barbiturates:
Barbituric acid is the parent compound for many central nervous system depressants. They are used as sedatives and anesthetics.
Barbituric Acid
N
O
N
O O
HH N
O
N
O O
HH
Phenobarbital
CH3CH2 C6H5
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13.12 Condensation Polymers
Condensation reactions between polyfunctional carboxylic acids and alcohols or amines produce a wide variety of polymers. They are called condensation polymers or step-growth polymers because of how they form.
Polymers formed from alkenes are called chain-growth polymers or addition polymers.
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13.12 Condensation Polymers
Polyesters are formed in reactions between diacids and diols.
Polyamides are formed in reactions between diacids and diamines.
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13.12 Condensation Polymers
Polyesters are formed in reactions between diacids and diols.
Polyamides are formed in reactions between diacids and diamines.
C
O
HO
C
O
OH+ HO CH2 CH2 OH
catalyst− H2O
terephthalic acid
ethyleneglycol
C
O
HO
C
O
O CH2 CH2 OC
O
C
O
O CH2 CH2 OH
n
Poly(ethylene terephthalate), PETE
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Important Polyesters
Polyesters are formed in reactions between diacids and diols.
Polyamides are formed in reactions between diacids and diamines.
C
O
C
O
O CH2 CH2n
Polyethylene terephthalate, PETE, "polyester" in plastics and fiber, Dacron
CH2 C
CH3
CO OH3C n
Poly(methyl methacrylate),PMMA, polymer used asglass, Lucite , Plexiglas
C
CH3
O C
O
O
CH3 n
Polycarbonate, polymerused as glass, very highimpact resistance
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13.12 Condensation Polymers
Synthetic and natural polyamides are important.Nylon 6,6 was developed by Wallace Carothers
of DuPont as a silk replacement in 1935.
HOC
(CH2)4C
OH
O O+ H2N (CH2)6 NH2
− H2O
HOC
(CH2)4C
N
O O
H
(CH2)6 NH
C
O
(CH2)4C
O
N
H
(CH2)6 NH
H
Adipic acid
Nylon 6,6
n
Hexane Diamine
285°
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13.12 Condensation Polymers
In the “nylon rope trick” polymer forms at the interface of a water solution of hexane di-amine and an organic solution of adipoyl chloride (adipic acid on steroids!).
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13.12 Condensation Polymers
Nylon 6 was developed in Germany. It is made by ring-opening, rather than condensation.
Nylons are very strong fibers because of inter-chain hydrogen bonding. There are regions of microcrystallinity, highly or-dered chain segments, in the material.
NC
O
H260°CN2
C(CH2)5
O
NC
H
O
(CH2)5 NH n
Caprolactam
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13.12 Condensation Polymers
From Wikipedia
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13.12 Condensation Polymers
Aramids are polyamides with aromatic com-ponents. They are even stronger than Nylon 6,6, and are used for demanding applications, such as armor.
CO
NH
NH
CO
C
n
Kevlar , high strength aramid Nomex , heat-resistant aramid
O
NH
C C
O
N
O
H
N
H n
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13.12 Condensation Polymers
Polyurethanes are polymeric carbamates. They are resilient, elastomeric, and can be made into foams. There are many structures, but most involve reactions between diisocyan-ates and diols.
+ HO R OH
Methylene diphenylisocyanate (MDI)
CH2
NC
O
NC
O
CH2
NC
NC
HH
O
O R O
O
O
n
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13.12 Condensation Polymers
Proteins and peptides are naturally-occurring polyamides formed from amino acids.
There are ~20 amino acids with different R’s.
Proteins are long polymers, n > 50 Peptides are short polymers, n < 50
HN
H
CH
R
C
O
OH HN
H
CH
R
C
O
N
H
CH
R
C
O
N
H
CH
R
C
O
OH
n
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Important Polyamides
Proteins and peptides are naturally-occurring polyamides formed from amino acids.
NC
H
O
(CH2)5 N
H
C
n
O
NC
(CH2)4C
N
O O
H
(CH2)6 N
H
C
O
Nylon 6,6
nH
Nylon 6
C
O
N
H
CH
R
C
O
N
Hn
Polypeptides,Proteins