Organic Nomenclature

Compounds in which carbon is the principal element.

Writing formulas. . .

Condensed: CH3CH(CH3)CH = CHCH(CH3)CH3

Kekule’

Skeletal

H C

H

H

C

H

H

H

Hydrocarbons. . . Contain only hydrogen and carbon. Types:

Alkane: single bonds; saturated (largest possible number of hydrogens/carbon atom. [CnH2n+2]

Alkene: one or more carbon-carbon double bond. Unsaturated hydrocarbon.

Alkyne: one carbon-carbon triple bond. Unsaturated

hydrocarbon. Aromatic: carbon atoms connected in a planar ring.

Unsaturated hydrocarbon.

H C

H

H

C

H

CH

H

H C

H

H

C

H

H

H

Hydrocarbons. . .

Relatively nonpolar. (covalent bonds)Insoluble in water. (like dissolves like)Less volatile with increasing molar mass.

(because of London dispersion forces)

Alkanes. . . [CnH2n+2]

Methane: CH4 major component of natural gas; home heating; gas stoves; hot water heaters

Ethane: C2H6

Propane: C3H8 used for home cooking and heating; gas grills

Butane: C4H10 disposable lighters and fuel canisters for gas camping stoves.

H C

H

H

C

H

H

H

Name consists of. . .

1. Prefix Where are the substituents?

2.Parent How many carbons in the longest chain?

3. Suffix Which family?

If two different chains of equal length are present: choose the one with the larger number of branch points as

the parent.

Rules for naming alkanes. . . Longest continuous chain of carbon atoms gives the root name

1. For alkanes, add –ane to the root:

Meth: C

Eth: C2

Prop: C3

But: C4

2. For alkanes beyond butane, use the Greek root for the number of carbons then add -ane to the end.

C-C-C-C-C-C = hexanepent=5; hex=6; hept=7; oct=8; non=9; dec= 10

Substituent

Group(s) added in place of a removed hydrogen.

Alkanes as a substituent group. . .

Alkyl substituents:

1. Remove a hydrogen from the alkane.

C2H6 is ethane

2. Drop the -ane and add -yl.

-C2H5 is ethyl

Positions of substituent groups are specified by numbering the longest chain sequentially. (Use the lowest number for the position of the substituent group)

The location and name of the substituent group is followed by root alkane name.

3-methylhexane

C

C-C-C-C-C-C

Substituents in alphabetical order.

Use di-, tri-, etc. to indicate multiple identical substituents.

Practice. . .write skeletal and condensed formulas.

2,3-dimethylhexane2-ethyl-3-methylpentane4-ethyl-3,5-dimethylnonane4-tert-butylheptane2,3-dimethylpentane

Cyclic Alkanes. . . CnH2n

CycloalkanesSmaller than five carbons, very reactive.Rings of carbon atoms. Isomers

Cis: both substituents are on the same side of the ring.

Trans: substituents are on opposite sides of the ring.

Reactions of Alkanes. . . .

Combustion: react with oxygen produce carbon dioxide and water

Substitution: halogen atoms replace hydrogen atoms

Dehydrogenation reactions:hydrogen removed forms double bond there unsaturated hydrocarbon is the product

Alkenes. . .

1. Root hydrocarbon (longest chain containing double bond) name ends in –ene.

2. More than three carbon atoms, the location of the double bond is indicated by the lowest numbered carbon atom in the bond. If equidistant: begin at end closer to substituent group. CH2=CHCH2CH3 1-butene CH3CH=CHCH3 2- butene

3. More than one double bond Indicate the position of each and use –diene, triene,

tetraene. . .

Cycloalkenes. . .

Name same as alkenes.Number so double bond is between C1

and C2 and the first substituent has the lowest number possible.

Practice. . .write the skeletal formula and name.

CH2=CHCH(CH3)C(CH3)(CH3)CH3

CH3CH2CH=C(CH3)CH2CH3

CH3CH=CHCH(CH3)CH=CHCH(CH3)CH3

Practice. . .

2-methyl-1,5-hexadiene3-ethyl-2,2dimethyl-3-heptene2,3,3-trimethyl-1,4,6-octatriene4-tert-butyl-2-methylheptane3,4-diisopropyl-2,5-dimethyl-3-hexene

Practice. . .

CH3

CH3

CH(CH3)2

CH3

CH3

Alkynes. . .

Unsaturated hydrocarbons contain atleast one triple carbon-carbon bond.

-yne replaces –ane. Begin numbering chain at end closest to triple

bond. More than one bond: -diynes, -triynes. Double and triple bonds: -enynes

Start numbering from end nearer first bond. (if there is a choice. Usually double bonds get lower numbers than triple.)

Practice. . .

CH3CH(CH3)C CCH(CH3)CH3

CH CC(CH3)(CH3)CH3

CH3CH=CHCH=CHC CCH3

CH3CH2C(CH3)(CH3)C CCH2CH2CH3

Practice. . .

Reactions of Alkenes and Alkynes. . .

Addition reactions: double bond broken and new bonds formed to atoms added. Hydrogenation reactions: addition of hydrogen atoms Halogenation: addition of a halogen

Elimination:one reactant splits apart to give two products.

Substitutions: two reactants exchange parts to give two new products.

Rearrangement:one reactant undergoes a reorganization of bonds and atoms to give a new product.

Aromatic Hydrocarbons. . .Benzene and its structural relatives

Monosubstituted benzene: named as other hydrocarbons, with benzene as parent name. If substituent larger than ring (six carbons) : benzene

becomes substituent group called phenyl.

Disubstituted benzene: ortho:1,2 meta-1,3 para-1,4

More than two: number the position of each substituent group.

Alcohols. . .

Alcohols: presence of an –OH (hydroxyl group)

Nomenclature: replace final -e of parent hydrocarbon

with –ol. (parent: longest chain containing –OH)

Position of –OH specified by number- lowest number. Classified by: number of hydrocarbon fragments

bonded to carbon where –OH group is attached. eg. C-C-C-C or C-C-C-C or C

C-C-C

Functional Groups

Alcohols. . . .

PolarHigher boiling points than expected from

molecular weights.Intermolecular attractions. –OH

extensive hydrogen bonding.

Practice. . .

CH3C(OH)(CH3)CH2CH2CH3

2methyl-2-pentanol

CH3CH(OH)CH2CH(OH)CH(CH3)2

5-methyl-2,4-hexanediol

Practice. . .

Practice. . .

2-ethyl-2-buten-1-ol

3-cyclohexen-1-ol

3-chlorocycloheptanol

1,4-pentanediol

Aldehydes. . .

Nomenclature: remove –e replace with –al. Longest chain as base name,must contain the

carbonyl group. Aldehyde carbon assigned number 1, when subtituent positions are listed in the name.

Bonded to at least one hydrogen atom. Number indicates position of carbonyl group.

Practice. . .

Practice. . .

CH3CHO

Ethanal

CH3CH2CHO

Propanal

CH3CH(CH3)CH2CH(CH2CH3)CHO

2-ethyl-4-methylpentanal

Ketones. . .

Contain carbonyl group bonded to two carbon atoms

Final –e replaced with -one. Longest chain with ketone group is the parent. Numbering begins at the end nearest the

carbonyl carbon.

Practice. . .

CH3CH=CHCH2COCH3

4-hexen-2-one CH3CH2COCH2COCH3

2,4-hexanedione CH3CH2COCH(CH3)2

2-methyl-3-pentanone CH3COCH2CH2CH2COCH2CH3

2,6-octanedione

Practice. . .

OHCCH2CH2CH2CHO

PentanedialCH3CH2CH(CH3)CH(CH2CH2CH3)COCH3

4-methyl-3propyl-2-hexanoneCH3CH=CHCH2CH2CHO

4-hexenal

Practice. . .

3-methylbutanal

3-methyl-3-butenal

4-chloro-2-pentanone

Carboxylic Acids. . .

Two systems: aldehyde and alcoholDerived from open chain alkanes:

Carboxyl carbon is always C1.Replace terminal –e of alkane with –oic

acid. -COOH group bonded to a ring, the suffix –

carboxylic acid is used. The carboxylic acid carbon is attached to C1 and is not itself numbered in this system.

Practice. . .

CH3CH(CH3)CH2CH2COOH

4-methylpentanoic acid

HOOCCH2CH(CH2CH3)CH2CH2CH(CH3)CH2COOH

3-ethyl-6-methyloctanedioic acid

Practice. . .

Practice. . .

(CH3)2CHCH2COOH

3-methylbutanoic acidCH3CHBrCH2CH2COOH

4-bromopentanoic acidCH3CH=CHCH=CHCOOH

2,4-hexadienoic acidCH3CH2CH(COOH)CHCH2CH2CH3

2-ethylpentanoic acid

Carboxylic Acids. . .

Strong hydrogen bonding has a noticeable effects on boiling points.

Much higher than corresponding alcohols.

Isomerism