Ch. 3 Review: Nomenclature: Organic Compounds

• Compounds of carbon--organic chemistry– If they have only C and H, hydrocarbons

– e.g. alkanes: methane CH4, ethane C2H6, propane C3H8

• general formula: CnH2n+2

– Know Table 3.7

• Functional Groups– R = hydrocarbon group

– e.g. alcohols: methanol CH3OH, ethanol C2H5OH

– e.g. amines: propyl amine, butylamine– Know functional groups in Table 3.8

Methanol (wood alcohol), CH3OH, is related to methane, CH4, by replacing one H with OH.

Organic chemistry -- Chapter 20

• Introductory Topics

Bonding & Structure -- Review Chapters 3, 9, and 10!!Types of Chemical Formulase.g. 2-propanol (iso-propanol)

!!! Always FOUR BONDS to Carbon !!!

H C

H

H

C

O

H

C

H

H

H

H

expandedstructuralformula

H3C CH

OH

CH3

orOH

CH3CHCH3

condensed structural formula

OH

fully condensedstructural formula

(missing C’s and H’s are understood)

“line drawing”

Isomerism• Isomers– different molecules with the same molecular

formulaStructural isomers--different pattern of atom attachment; different connectivity

Stereoisomers—same atom attachments (connectivity), different spatial orientation

Rotation about a single bond is not isomerism!!

Structural Isomers• Structural Isomers -- same chemical formula, but

different arrangement (connectivity) of atomse.g. C3H8O - 3 isomers (2 alcohols, 1 ether)

Number of possible isomers can be very large, e.g.

C3H8 C4H10 C5H12 C6H14 C8H18 C10H22 C20H42

1 2 3 5 18 75 > 105

CH3 CH2 CH2 OH

H3C CH

OH

CH31-propanol2-propanol

ethyl methyl ether

CH3 CH2 O CH3

Stereoisomers• Stereoisomers—same atom attachments (connectivity),

different spatial orientation• Optical isomers (enantiomers)—are molecules that

are nonsuperimposable mirror images of each other

• Geometric isomers—are stereoisomers that are not optical isomers, e.g. cis and trans

Chiral Molecules• Are molecules that have nonsuperimposable mirror

images– If 4 different groups are attached to carbon, it will be

chiral– Chiral molecules will rotate plane-polarized light– Most physical properties are identical, but in a chiral

environment enantiomers behave differently

7

Isomerism; Overview

Many Possible CompoundsA Tremendous Variety of organic molecular structures and

properties are possible, e.g.:

H

C

H

C

H

Cl

C

H

H

C

H

Cl n

CH3 C

O

OH

COH

O

O C

O

CH3

vinyl chloride poly(vinyl chloride) “PVC”

acetic acid

aspirin

More Organic Compounds

N

O

CH3

O

CH3

N

N

CH3

CH3 N

H

H

CaffeineC8H10N4O2

methylamine

fortunately, the subject is very systematic !and is readily classified by “organic functional groups”

Hydrocarbons• Alkanes CnH2n+2

CH4 methane C5H12 pentane

C2H6 ethane C6H14 hexane

C3H8 propane C7H16 heptane

C4H10 butane C8H18 octane, etc….

alkyl groups:

methyl CH3

ethyl CH3CH2

phenyl C6H5

H C

H

H

H C

H

H

C

H

H

Alkane Nomenclature1. Name parent chain--longest continuous chain2. Number parent chain

-- First branch gets lowest possible number

3. Name & number branches4. Order branches

-- Alphabetical order-- Multiple identical substituents get prefix

CH3CH2CHCHCHCH2CHCH3

CH3 CH3 CH3

CH2CH3

5-ethyl-2,4,6-trimethyloctane

C N

Br

5-bromo-2-cyano-4-methylheptane

Samples:

(see book for detailed “rules” and other functional groups)

Reactions of Alkanes (generally unreactive)

• Combustion -- fuels!e.g. C5H12(l) + 8 O2(g) --> 5 CO2(g) + 6 H2O(l)

• Free radical substitution (not selective!) C2H6(g) + Cl2(g) --> C2H5Cl(g) + HCl(g)

• Dehydrogenation (reverse rxn is more common!) C2H6(g) --> H2C=CH2(g) + H2(g)

• “Cracking” of hydrocarbons (petroleum industry)

needs heat!

needs heat and/or pressure!

needs heat!needs catalyst!

Alkenes ~ C=C double bond

CnH2n (with one double bond)

• Geometric isomers are possible, e.g.:

– Restricted C=C bond rotation– Trigonal planar geometry at C=C carbons– sp2 hybridization at C=C carbons

• Nomenclature (C=C bond takes preference)

H3C

C

H

C

CH3

H

H

C

H3C

C

CH3

H

cis-2-butene trans-2-butene

CH3CH2CHCH2CH=CCH3

CH3 CH3

2,5-dimethyl-2-heptene cyclohexene

Reactions of Alkenes

addition to double bond

RCH=CH2 + HX --> RXCH-CH3

R

C

H

C

H

H

H X

R

C

H

C

H

H

HX

R

C

H

C

H

H

HX

X

RHC CH3

+

≡

Markovnikov’s rule ~ “them that has, gets”(H goes on the C that already has the most H’s)

Addition of non-polar reagents (H2, Br2, etc) also occurs

Alkynes ~ C≡C Triple Bond

CnH2n-2 (with one triple bond)

• linear geometry at C≡C carbons• sp hybridization at C≡C carbons• no “cis-trans” isomers• similar addition reactions to alkenes

(stepwise addition can occur)

R C C H

X

C

R

C

Y

H

X

C

X

C

Y

Y

HRXY XY

Aromatic Hydrocarbons(benzene and its derivatives)

Benzene ~ C6H6

• planar 6-membered ring (especially stable)• all C-C distances equivalent• sp2 hydridization at all carbons• delocalized set of 3 double bonds (6 electrons)

other common aromatic hydrocarbons:

napthalene anthracenes

Aromatic Nomenclature• Aromatic ring as substituent

– Phenyl (C6H5–)

– Benzyl (C6H5CH2–)

• Monosubstituted benzene– (name of substituent)benzene– Some common “trivial” names

• Toluene• Phenol

• Polysubstituted benzene– Assign numbers to substituents

H2C CH CH2 CH2 CH3CH

4-phenyl-1-hexene

CH2CH2CH3

propylbenzene

F

Br1

23

1-bromo-3-fluorobenzene

Aromatic Substitution Rxns• Substitution Reactions of Aromatic Hydrocarbons (never

addition!)

H

H

X

X

H

H

X

H

NO2

H

X2

X2

X = Cl, Br

HNO3

(H+ catalyst)

( NOT aromatic! )

needs catalyst!

Organic Functional Groups

Family Characteristic Structural Feature

Examples

Hydrocarbons alkanes alkenes alkynes aromatic

only single bondsC=CC≡C

benzene ring

CH3CH3

CH2=CH2

HC≡CH

Alcohols* R-O-H CH3CH2OH

Ethers* R-O-R’ CH3OCH3

* structures like waterH

O

H

More Organic Functional Groups

Family Characteristic Structural Feature

Examples

Aldehydes

Ketones

Carboxylic Acids

Esters

“carbonyl” compounds

R C

O

H

R C

O

R'

R C

O

OH

R C

O

OR'

H3C C

O

H

H3C C

O

CH3

H3C C

O

OH

H3C C

O

OCH3

C

O

More Organic Functional Groups

Family Characteristic Structural Feature

Examples

Amines: 1º 2º 3º

RNH2

RNHR’RNR’R”

CH3NH2

(CH3)2NH

(CH3)3N

Amides R C

O

N

H (R')

H (R")H3C C

O

NH2

N

Alcohols (organic derivatives of H2O)

NomenclatureAlcohols, R-O-H

R = CH3 methanol

R = CH3CH2 ethanol

R = CH3CH2CH2 1-propanol (n-propanol)

CH3CHCH3

OH

2-propanol(iso-propanol)

OH

3,7-dimethyl-4-octanol

OH

phenol

Reactions of AlcoholsOxidation

H

CR

H

O H

H

CR

R

O H

R

CR

R

O H

R C

O

H

R C

O

R

primary

[O]

– “H2”aldehyde

secondary

[O]

– “H2”ketone

[O]No Reaction

[O] = oxidizing agent, e.g. Cr2O72–

tertiary

More Reactions of Alcohols

R C

H

CH2

OH

H

R

C

H

CH2

Elimination

alcohol

H+

alkene

+ H2O

Substitution

RCH2—OH + H—X – H2O

RCH2—Xalcohol

X = Cl, Br, Ialkyl halide

Aldehydes and Ketones

Nomenclature

H C

O

H H3C C

O

H CH3CH2 C

O

H

H3C C

O

CH3 H3C C

O

CH2CH3

O

methanal(formaldehyde)

ethanal(acetaldehyde)

propanal

propanone(acetone)

butanone(methyl ethyl ketone) 5-methyl-3-heptanone

Reactions of Aldehydes and Ketones

Hydrogenation (reduction) of aldehydes and ketones

R C

O

H

R C

O

R'

R C

O

OH

R C

OH

H

H

R C

OH

R'

H

R C

O

H

aldehyde

“H2”

primary alcohol

ketone

“H2”

secondary alcohol

Oxidation of aldehydes (very easy!)

aldehyde

[O]

carboxylic acid

Carboxylic AcidsNomenclature of Acids

H C

O

OH H3C C

O

OH C

O

OH

CH3CH2CH2 C

O

OH

H3C C

O

OH H3C C

O

ONa

methanoic acid(formic acid)

ethanoic acid(acetic acid) benzoic acid

butanoic acid

CH3CH2CH2CO2H(condensed formula)

Salts of Acids

acetic acid

NaOH

H2O

sodium acetate

Condensation Reactions

• a condensation reaction is any organic reaction driven by the removal of a small molecule, like water

• esters are made by the condensation reaction between a carboxylic acid and an alcohol

the reaction is acid catalyzed

• acid anhydrides are made by the condensation reaction between 2 carboxylic acid molecules

the reaction is driven by heat

R C

O

OH OH C

O

R' R C

O

O C

O

R'

+ + HOH

Esters

Nomenclature of Esters

R C

O

O R' H3C C

O

O CH2CH3

CH3CH2CH2 C

O

O CH2CH3 C

O

O CH3

H O R'

O

CR O H R C

O

O R'

alkyl group

acid name

-ateethyl acetate

ethyl butanoatemethyl benzoate

Formation of Esters (from acid + alcohol)

+ + H2O

EthersEthers R – O – R’

CH3CH2–O–CH2CH3 diethyl ether

CH3–O–CH2CH2CH3 methyl propyl ether

• Ether Synthesis:

R–O–H + H–O–R R–O–R

H+

– H2O

Amines(organic derivatives of NH3)

H3C N H

H

H3C N H

CH3

H3C N H

CH2CH2CH3

NH2

NH2

methylamine dimethylamine methylpropylamine

2-aminohexane aniline

Like ammonia, amines are weak bases:

RNH2 + H+ RNH3+

Amides

Acid derivatives (e.g. 1º amides: –NH2 instead of –OH)

O

CR O H H NH2R C

O

NH

H+ + H2O

Nomenclature

R = CH3

R = CH2CH2CH2CH3

ethanamide

pentanamide, etc.

amides (unlike amines) are generally not basic (due to e- withdrawing effect of the C=O group)

Sample Questions

(1) Write complete, systematic names for:

H3C C CH CH CH3

CH2CH2H3C C N

C

O

O CH

CH3

H2C CH3

H C

O

CH2 CH2 CH CH2 CH3

Sample Questions, cont.(2) Write complete, specific structural formulas for all of the

organic reactants and products in the reaction.

an ester sodium acetate + 3-pentanol

(3) Show, with specific structures and reactions, how the following compound can be prepared in three steps starting with the appropriate alkyne.

NaOH

H3C C

O

CH

CH3

CH3

Answers1. 2-cyano-4-methyl-3-heptene 2-butylbenzoate 4-phenylhexanal2.

H3CC

O

O

CH

CH2

CH2

CH3

CH3 H3CC

O

ONa+ OH

H C C CH

CH3

CH3

H

C

H

C

H

CH CH3

CH3

H

C

H

C

H

CH CH3

CH3

H C

H

H

C

OH

H

CH

CH3

CH3

NaOH+

3.+ H2

cat,

pressurestep 1

+ H2O acid catstep 2

Answers, cont.

3., cont.

H C

H

H

C

OH

H

CH

CH3

CH3

[ox]H3C

C

O

CHCH3

CH3

Organic Polymers

Polymers -- macromolecules made up of many repeating units called monomerse.g. polystyrene is formed via the polymerization of the monomer styrene:

e.g. some rings can open to form polymers:

HC CH2 CH CH2 n

O CH2 CH2 CH2 CH2 On

h

styrene polystyrene

n ~ 103 - 106

Methods of PolymerizationAddition (very common -- works with most alkenes)

CH2=CH2 + CH2=CH2 + CH2=CH2 etc….

---CH2–CH2–CH2–CH2–CH2–CH2--- =

• requires an initiator (e.g. a catalyst or UV light) to start the “chain” reaction

CH2n

More Methods of PolymerizationCondensation (common for polyesters and polyamides)

a small molecule (e.g. H2O) byproduct is formed

X-A-Y + X-B-Y Ring-Opening (uncommon except for polyethers and

most inorganic polymers, e.g. silicones)

A Bn

A B A B A B A

– XY

A B

etc…

Common Addition PolymersMonomer Polymer

CH2=CH2—CH2–CH2—n

ethylene polyethylene

CH=CH2

styrene

—CH–CH2—n

polystyrene

CH=CH2

Cl vinyl chloride

—CH–CH2—n

—CH–CH2—n

Clpoly(vinyl chloride) ~ PVC

CH=CH2

N≡C N≡Ccyanoethene “Orlon”

One More Common Addition Polymer!

Addition polymerization of dienes

H2C C

CH3

CH CH2CH2 C

CH3

CH CH2n

“isoprene”(2-methyl-1,3-butadiene)

“natural” rubber

Common Condensation Polymers

Polyesters

C

O

C

O

O CH2 CH2 O

n

H O C

O

A C

O

O H H O B O H

C

O

A C

O

O B On

A B CH2 CH2

+diacid diol

polyester

– H2O

e. g. = =

“Dacron”

Sample QuestionWrite a complete structural formula of the organic polymer

that is produced in each reaction. State whether the polymerization process is addition, condensation, or ring-opening.

CHO

O

COH

O

O

CH3

CH2 CH

C N

+ HO-CH2CH2-OH

Answer

a. condensation

b. ring-opening

c. addition

d. addition

O

n

CH2 CH

C N

n

n

O

O O

O CH2CH2

n