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