Nomenclature

CH3CH2CHCH2CH2CH2OH

CH3

4-methyl-1-hexanol

OHor

Locant prefix locant parentsuff ix

Nomenclature of AlcoholDetermine the longest chain of carbon to

which the hydroxyl is directly attached and name itDrop the final -e to suffix –olE.g methane methanol

Number the longest chain so that the carbon atom bearing the hydroxyl group will have the lowest number.

CH3CH2CH2OH3 2 1

1-propanol

CH3CHCH2CH3

OH

1 2 3 4

2-butanol

CH3CHCH2CH2OH

CH34-methyl-1-pentanolor 4-methylpetan-1-ol

1234

OH

OH

OHpropyl alcohol

Butyl alcoholsec-Butyl alcohol

OHOH

tert-Butyl alcohol isobutyl alcohol

ExampleDraw bond-line formulas and give IUPAC

substituted names for all of the isomeric alcohol with the formula C4H10O

4.4 Monocyclic CompoundCycloalkanes with only one ring are name by

attaching the prefix “cyclo-” to the name of the alkanes

cyclopropane cyclobutane cyclopentane

Cyclic alkanesIf a cyclic alkane and one substituent is

present, no need to designated position of substituent

isopropylcyclohexane bromocycloheptane

Br

tert-butylcyclopentane

Cyclic alkanesIf a cyclic alkane and two substituents are

presented, we number the ring beginning with the substituent first in the alphabet and number in the direction that gives the next substituent the lower number possible

1-ethyl-3-methylcyclohexane

Cl

Br

1-bromo-3-chlorocycloheptane

Cyclic alkanesIf a cyclic alkane and three or more

substituents are presented, we begin at the substituent that leads to the lowest set of locants

lc

Br

2-ethyl-1,4-dimethylcyclohexane 3-bromo-5-chloro-2-ethyl-1-methylcycloheptane

Cyclic alkanesWhen a single ring system is attached to a

single chain with a greater number of carbon atoms, or when more than one ring system is attached to a single chain, then

1-cyclobutylpentane 1,3-dicyclopropylpropane

4.4 Bicyclic compoundsA compound is considered bicyclic is when it

contains two fused or a bridged ringThe name of bicyclicalkane is corresponding

to the total number of carbon presented.

CH2

Bridge

bicycloheptaneorbicyclo[2.2.1]heptane

Fused

bicyclo[1.1.0]butane

Bicyclic alkanesIf substituents are present, we number the

bridge ring system beginning at on bridge-head, proceeding first along the longest bridge to the other bridge-head. The shortest bridge is named last

CH3

8-methylbicyclo[3.2.1]octane8-methylbicyclo[4.3.0]nonane

4.5 Nomenclature of Alkenes and CycloalkenesRules for naming alkenes

Identify and name the longest chain of carbon atoms that contain C=C

Parent name contains suffix -eneNumber the carbon chain from one to the

other, so as to give the lowest number to a double bond Designated the location of the double bond to the

parent nameIdentify substituents and their locations

4.5 Nomenclature of Alkenes and CycloalkenesRules for naming cycloalkenes

Identify and name the longest chain of carbon atoms that contain C=C

Parent name contains suffix -eneNumber the carbon chain from one to the

other, starting with the double bondIdentify substituents and their locations

4.5 Nomenclature of Alkenes and CycloalkenesName compounds containing a double bond

and an alcohol as alkenol (cycloalkenol)Give the alcohol carbon the lower number

OH

12345

4-methyl-3-penten-2-olor 4-methylpent-3-en-2-ol

OH

2-methyl-2-cyclohexen-1-ol

1

2

3

4.5 Nomenclature of Alkenes and CycloalkenesTwo common alkenyl groups

CH2 CH H2C CHCH2

Vinyl group Allyl group

H

H

H

Br

Bromoetheneor vinyl bromide Ethenylcyclopropane

or vinylcyclopropane

OH

3-allylcyclohexanol

4.5 Nomenclature of Alkenes and CycloalkenesIf two identical substituents are on the same

side of the double bond, the compound is designated cis

If they are opposite, the compound is designated transH

Cl

H

Cl

cis-1,2-dichloroethene

Cl

H

H

Cl

trans-1,2-dichloroethene

Nomenclature of AlkynesRules for naming an alkynes are similar to

alkene BUTParent name ends with -yne

C C HH

Ethyneor acetylene 2-pentyne

OH

23

451

2-methyl-4-pentyn-2-ol

ExampleName the following compound

Draw the geometric isomers of 2-butene. Label them cis and trans

a. b. c.

Cl

OH

Nomenclature of AlkynesMonosubstituted acetylene or 1-alkyne are

called terminal alkynes

C C HR

Ethyneor acetylene

Acetylenic hydrogen

C CR

Alkynide ionH

4.7 Physical Properties Alkanes and CycloalkanesBoiling point: increases with increasing molecular weight - unbranched molecules (homologous series)Branched alkanes have lowers boiling point - affected by van der Waals forces

4.7 Physical Properties Alkanes and CycloalkanesMelting Points: - increasing but does not show the same smooth curve - alternation from odd and even number of carbon atoms - alkane chains with an even number of carbon atom pack more closely in the crystalline state higher mp cycloalkanes also have higher m.p

4.7 Physical Properties Alkanes and CycloalkanesDensity: Alkanes and cycloalkanes are the

least dense of all group in organic compound.E.g < 1.00 g/ml at 4oC

Solubility: alkanes and cycloalkanes are almost insoluble in waterDue to their low polarity and inability to form

H-bond“like dissolves like”

4.7 Physical Properties Alkanes and CycloalkanesRecall

Sigma (σ) bond Pi (π) bond

Created when “head on” overlap occurs of orbitals

Created when “side on” overlap occurs of orbitals

4.7 Physical Properties Alkanes and CycloalkanesOnly sigma (σ) bond can undergo rotation

about that bond with respect to each otherEach possible structure that result from

rotation of group about the signma bond is called confomormational isomers

Types: Newman projection formula and sawhorse formula

Newman projection

Sawhorse formula

Conformational isomersEclipsed conformation Staggered conformation

Each hydrogen on one carbon as close as possible to one hydrogen on the other carbon

Hydrogen on one carbon as far from the hydrogen from other carbon

H

HH

H

HH

EclipsedC C

HH

HH

H H

Electron repulsion

H

H H

H

HH

60o - dihedral angle

staggered

Potential energy diagram

Conformational isomers G is a group or atom other than hydrogen

Barriers to rotation are somewhat larger

G

H H

G

HH

H

H G

G

HH

conformers like these cannot be isolated except at extremely low temperature

H

CH3

H

H

CH3

H

HH

CH3 CH3

HH

H

HH3C

HH

H3C

H

CH3

HH

CH3

H

IAn anti staggered

IIan eclipsed

IIIa gauchestaggered

IVVVI

ExampleUsing Newman projections to draw out all

possible conformations of 1,2-dibromomethane

ExampleDraw a plot of energy versus dihedral angle

for the conformation of 2-methylbutane about the C2-C3 bond

1 2 34

Stereoisomers and Conformational StereoisomersStereoisomers have the same molecular

formula and connectivity but different arrangements of atoms in 3-D

Conformational Stereoisomers: Stereoisomers that are interconvertible with one another by bond rotation

The Relative Stabilities of Cycloalkanes: Ring StrainCarbon chains are confined in rings,

cycloalkanes are much less flexible than monocyclic alkanes.Strain energy is measure from the amount of

heat that is produced from combustion reactionRing strain describe the destabilization of a

cyclic molecule