2-1 chapter 2 saturated hydrocarbons constitutional isomers iupac nomenclature conformations...

2-2-11

Chapter 2

H3C

CH3

H

H OH

CH

H3C F

HO

CH

H3CF

O

CO

H3C

H

OH

O

CO

H3C

OH

H

+

+

XH

H2 / M

Cl

IC

H

H3C D

NC

CH

H3CD

(-):CN:

CH2

OH O

HCH3

CH3

H

Br Mg CH3

δ+ δ−

LiCu

2

saturated hydrocarbonsconstitutional isomers

IUPAC nomenclatureconformations

cis/trans isomers

nomenclature refinementfunctional groups

reactions, sources, properties

2-2-22

Chapter 2

H3C

CH3

H

H OH

CH

H3C F

HO

CH

H3CF

O

CO

H3C

H

OH

O

CO

H3C

OH

H

+

+

XH

H2 / M

Cl

IC

H

H3C D

NC

CH

H3CD

(-):CN:

CH2

OH O

HCH3

CH3

H

Br Mg CH3

δ+ δ−

LiCu

2

saturated hydrocarbonsconstitutional isomers

IUPAC nomenclature - continuedconformations

cis/trans isomers

nomenclature refinementfunctional groups

reactions, sources, properties

cp

42

2-2-33StructureStructure

HydrocarbonsHydrocarbons:: compounds only Cs and Hs

Saturated hydrocarbon:Saturated hydrocarbon: only single bonds

C

H CH

H

HH

C

C HH

H

HH

alkanealiphatic hydrocarbonacyclic saturated hydrocarbon

open or “linear” chain, saturated hydrocarboncp qz

2-2-44HydrocarbonsHydrocarbons

H-C-C-H

H

H

H

H

HydrocarbonsCs,Hs only

Alkanes

Only C-Csingle bonds

Class

C-Cbonding

ethane

Saturated Unsaturated

all C sp3

H-C C-HH

C CH

H H

triple bond(s)

structureslike:

Alkenes Alkynes Arenes

double bond(s)

sp2-sp2; π sp-sp; 2π n(sp2-sp2; π)

cp qz

2-2-55

CH4 methane (109.5o bond angles)

Structure of alkanes (aliphatic hydrocarbons, acyclic saturated hydrocarbon):

open or “linear” chain, saturated hydrocarbons

H

C

H

CH

H

HH

CH3CH3 ethane (109.5o)

propane ( 109.5o)

CnH2n+2 (alkanes)

CH3CH2CH3

H

HC

H

H

cp qz

2-2-66

2.2 methane, ethane, propane - 1 structure, but ….

C4H10 has 2 forms, same molecular formula but different arrangement - isomers

HC

CC

CH

H H

H

H

H

H

HH

HC

CC

H

HH

H

H H

C

HHH

bpt. -0.5oC -11.6oC

different connectivity - constitutional isomers

cp qz

2-2-77

CH3CH2CH2CH2CH3

C5H12

CH3CHCH2CH3

CH3

CH3-C-CH3

CH 3

CH3

Note example (problems) pg 59, 60

CH3 CH CH2

CH3

CH3

the same

cp qz

2-2-88Constitutional IsomerismConstitutional Isomerism

4,111,846,763

4,347

75

31

Constitutional Isomers

MolecularFormula

CH4

C5H12

C10H22

C15H32

C30H62

36,797,588C25H52

UNIQUE NAME for each?

IUPAC nomenclature system

cp qz

2-2-99IUPAC nomenclature: alkIUPAC nomenclature: alkananee

number of carbons (alk)+(ane) saturated HC

undec-dodec-

tetradec-pentadec-hexadec-heptadec-

nonadec-eicos-

tridec-

11121314151617

octadec- 181920

Prefixmeth-eth-prop-but-pent-hex-

oct-non-dec-

1234567hept-89

10

Carbons CarbonsPrefix

prefix+suffix

cp qz

2-2-1010Nomenclature - IUPACNomenclature - IUPAC

ParentParent:: longest (most important) carbon chain

substituent:substituent: group off parent chain

alkyl group:alkyl group: a substituent carbon gp

R- symbol

CH4 CH3-

CH3CH3 CH3CH2-ethane ethyl

alkane alkyl or R- group

methane methyl

cp qz

2-2-1111

CH3CHCH3

CH31

2 3

Nomenclature - IUPACNomenclature - IUPAC

1. name (prefix + suffix) longest HC chain

( parent or root name)

2. substituent(s) given name and number

propane2-methylpropane

3. 1 substituent, number chain to give it the lower number

CH3CH2CH2CHCH3

CH3

2-methylpentane

123

45 5

432

1

(not 4-methylpentane)

cp qz


4. Identical Substituents: number from the end that gives the lower number

12

34

56

2,4-dimethylhexane

65

43

21not 3,5-dimethylhexane

Combine like substituents: di-, tri-, tetra-, etc.

Use commas to separate position numbers

cp qz

2-2-1313Nomenclature - INomenclature - IUPACUPAC5. Different substituents

- list them in alphabetical order- number -lower number to the 1st -substituent

[branch alkyl

group R group]

12

34

5 67

3-ethyl-5-methylheptane

76

54

3 21not: 3-methyl-5-ethylheptane

5-ethyl-3-methylheptane

cp qz


6. di-, tri-, tetra-, etc. are not used in alphabetization

7. alphabetize substituents and then insert these prefixes

12 3

45

6

4-ethyl-2,2-dimethylhexane

(not 2,2-dimethyl-4-ethylhexane)

cp qz

2-2-1515

nonane

C

CC

C

CC

CC

CC

C

CHH H

C

HH

HH

H H

H

H

HHH

H

H

H

HH

HH

H

H

H

HH

HH

C

CC

C

CC

CC

CC

C

CHH H

C

HH

H H

H H

H

H

HHH

H

H

H

HH

HH

H

H

H

H H

HH

alkane

dimethyl

ethyl

-ethyl- , -dimethylnonane6-ethyl-3,3-dimethylnonane

cp qz

2-2-1616C & H ClassificationC & H Classification, not nomenclature, not nomenclature

Primary (1°C)Primary (1°C) C bonded to 1 other C and 3Hs (alkane or 2Hs func. gp)

[“methyl” group]C

CC

C

CC

CC

CC

C

CHH H

C

HH

H H

H H

H

H

HHH

H

H

H

HH

HH

H

H

H

H H

HH

Secondary (2°)Secondary (2°) C bonded to 2 Cs (2H)

[“methylene” gp.]

Tertiary (3°)Tertiary (3°) C bonded to 3 Cs (1H)

[“methine” ]

Quaternary (4°)Quaternary (4°) C bonded to 4 Cs

cp qz

2-2-1717Cycloalkanes CCycloalkanes CnnHH2n2n

Line-angle drawings

H2C

H2C CH2

CH

CH2

CH

CH3

CH3

C8H16

C

C CC

CC

C

C

cp qz

2-2-1818CycloCycloalkanesalkanes

nomenclature• open-chain name with cyclo- cyclo- prefix• name each substituent on the ring

1 substituent, no number

2 substituents, number by alphabetical priority

- list substituents in alphabetical order3+ substituents, number to give lowest set of numbers

- alphabetical order

cp qz

2-2-1919

CYCLOALKANES substituent + alk + ane

butyl + ethyl + cyclo + hept+ ane

alphabetical numbering priority

substituent + cyclo + alk + anecyclo +

1-butyl-4-ethylcycloheptane

cp qz

2-2-2020CycloalkanesCycloalkanesExample: (1) Incorrect name: 1,4-dimethyl-3-ethylcyclohexane

write the correct name.

hint - draw, rename

(c) (d)

c,d substituent(s) on substituents

(2) Write an IUPAC name for the following:

(a) (b)

cp qz

2-2-2121

dimethyl

Nomenclature

nonanecyclopropyl

6-cyclopropyl-2,4-dimethylnonane

CC

CC C

C

CH3C

CH3

H3C

H H

H H

H

H H

HCH3

H

H

H

return to more nomeclature details later

cp qz

2-2-2222Bicycloalkanes ---- outBicycloalkanes ---- out

Bicycloalkane:Bicycloalkane: an alkane that contains two rings that share two carbons

Spiroalkane two rings share one carbon

Bicyclo[4.4.0]decane(Decalin)

Bicyclo[2.2.1]heptane(Norbornane)

cp qz

2-2-2323

H3C

ConformationsConformations:: 3-D arrangements of atoms in a molecule from rotation/twisting about single bonds

Newman projectionNewman projection:: conformational view along a carbon-carbon bond

H3CH3C

H3CH3C

cp qz

2-2-2424ConformationsConformationsStaggered Staggered conformation:conformation: atoms/groups on 1 carbon are

as far apart as possible from the atoms/groups on adjacent carbon

H

H H

H H

H

= 60o

cp qz

2-2-2525ConformationsConformations

Eclipsed Eclipsed conformation:conformation: atoms/groups on 1-C in closet approach to atoms/groups on adjacent C

H

H H

H

HH

same plane= 0o

cp qz

2-2-2626ConformationsConformationsTorsional strain or eclipsed interaction strainTorsional strain or eclipsed interaction strain

strain (E) arises from nonbonded atoms rotate from staggered to eclipsed conformations

+12.6 kJ/mol

cp qz


Ethane as a function of dihedral angle

cp qz


anti conformationanti conformation• a conformation about a single bond in which the groups

lie at a dihedral angle of 180°

CH3

H H

H H

CH3

cp qz


Steric strainSteric strain (nonbonded interaction strain)(nonbonded interaction strain): when atoms separated by 4 (more) bonds are forced closer

Angle strain:Angle strain:when a bond angle must compressed or expanded from 109.5o

calculate total strain - determine the lowest energy conformation ( molecular mechanics )

cp qz


• conformations of butane as a function of dihedral angle

cp qz

2-2-3131CyclopropaneCyclopropane

angle strain:angle strain: bond angles compressed (109.5° 60°)

torsional strain:torsional strain: all 6Hs eclipsed

strain energy highH

H

H

H

H

H

cp qz

2-2-3232CyclobutaneCyclobutane

puckering torsional strain

slight angle strain

H

H

H

H

H H

H H

H H

HH

H

H

HH

net - puckered (butterfly) minimum energy conformation

but strain energy highcp qz

2-2-3333CyclopentaneCyclopentane

“envelope” - torsional strain

slightly angle strain

envelope ~ 1/4th strain energy of cyclopropane

H

H

H

H

H H

H

H HH

H H

H

HH

H

H

H

H

H

cp qz

2-2-3434Cyclohexane - chair conformationCyclohexane - chair conformation

Bond bond angles - 110.9° StaggeredNo angle or torsional strainNo angle or torsional strain

six Hs are axial and six equatorial

H

H

H

H

H

H

HHH

H H H

cp qz

2-2-3535

cyclohexane 2 equivalent chair conformations

Flip converts

6 equatorial 6 axial

6 axial Hs in one chair 6 equatorial Hs in other

H

H

H

H

H

H

HHH

H H H

H

HH

H

H

H

H H

H H H

H?

cp qz

2-2-3636

Equatorial and axial methyl conformations

MethylcyclohexaneMethylcyclohexane

CH3

H

H

H

H

H

H

H

H H

H

H

H

H

H

H

H

H

H

HH

H

CH3

H +7.28 kJ/mol

94 / 6

cp qz

2-2-3737Cis,TransCis,Trans Isomerism Isomerism

Stereoisomers - Stereoisomers - compounds with: same molecular formula and connectivity

different orientation of atoms in space

cis,cis,transtrans isomersisomers - stereoisomers with:2 groups on same or opposite side of geometric

restriction (i.e. ring, double bond).

cp qz

2-2-3838CisCis,,TransTrans Isomerism Isomerism

trans-1,4-dimethylcyclohexane

cis-1,4-dimethylcyclohexane

CH3

H3C

H H

H3C

CH3H

H

cp qz

2-2-3939CisCis,,TransTrans IsomerismIsomerism

trans-1,4-dimethylcyclohexanediequatorial-methyl chair more stable by 14.56 kJ/mol

[2 x 7.28]

H

CH3

H

CH3

H

H

H H

H H H

HH

H

H

H

H

H

HHH3C

H H CH3

cp qz

2-2-4040ciscis,,transtrans isomerism isomerism

cis-1,4-dimethylcyclohexane

CH3

H

H

H

H

H

HHH

H H CH3 H

HH

CH3

H

H

H3C H

H H H

H

same energy

Note! flip reverses axial-equatorial but……. cis or trans doesn’t change

cp qz

2-2-4141CycloalkanesCycloalkanes

(2) Write an IUPAC name for the following:

(a) (b)

(c) (d)

c,d substituent(s) on substituents qz


branched substituents

1-methylethyl (isopropyl)

propyl

CH3

-CH2CH2CH3

-CHCH3

1,1-dimethylethyl (tert-butyl)

1-methylpropyl (sec-butyl)

2-methylpropyl (isobutyl)

butyl

CH3

CH3

CH3

CH3

-CH2CH2CH2CH3

-CH2CHCH3

-CHCH2CH3

-C-CH3

Formula Formula

qz

2-2-4343

qz

1-tert-butyl-3-isobutylcyclopentane

Draw the structure of:

trans-1-tert-butyl-3-isobutylcyclopentane

H

H

H

H

OR

2-2-4444refinement of IUPAC Parentrefinement of IUPAC Parent

prefix-infix-suffixinfixinfix - nature of C-C bond(s)

suffixsuffix - class (functional group)

one (more) triple bond(s)

one (more) double bond(s)

single bonds

-yn-

-en--an-

Nature of C-C Bond(s)Infix

prefix-suffix

Chapter 4

qz

2-2-4545IUPAC - GeneralIUPAC - General

prop-enen-e = propene

eth-anan-ol = ethanol

but-anan-one = butanone

but-anan-al = butanal

pent-anan-oic acid = pentanoic acid

cyclohex-anan-e = cyclohexane

eth-ynyn-e = ethyne

eth-anan-amine = ethanamine

CH3CH=CH2

CH3CH2OH

CH3CH2CH2CH2COH

O

HC CH

CH3CH2CH2CH

O

CH3CCH2CH3

O

CH3CH2NH2

qz

2-2-4646Alkanes - what are they good for?Alkanes - what are they good for?

MAJOR - energy, to do work:

initiationCH4 2O2 CO2 2H2O+ +H0

-212 kcal/mol

H3C X2 H-X+ +H H3C X + heat + otherinitiation

some products

other - oils, lubricants

qz

2-2-4747Sources of AlkanesSources of Alkanes

Natural gas • 90-95% methane

Petroleum• gases (bp below 20°C)• naphthas, including gasoline (bp 20 - 200°C)• kerosene (bp 175 - 275°C)• fuel oil (bp 250 - 400°C)• lubricating oils (bp above 350°C)• asphalt (residue after distillation)

Coalqz

2-2-4848Physical PropertiesPhysical Properties

Intermolecular forces of attraction (example)strong: ion-ion (Na+ and Cl- in NaCl)

ion-dipole (Na+ and Cl- solvated in aqueous solution)medium:dipole-dipole and hydrogen bondingweak: dispersion forces (very weak electrostatic

attraction between temporary dipoles)

qz

2-2-4949

Branching (ball-like)less surface to interact: bpt, mpt, density

less

HC

CC

CH

H H

C

H

H H

H H

HC

CC

CC

H H

HH

H H

HH

HH

H

H

HH

δ+δ-

δ+

δ-

δ+δ-

Longer or Straight Chains - more interactions along chain.

HC

CC

H

H H H H

C CH

H H H

H

CHH

H

HC

CCH

HHHH

CC

H

HH

H

H

CHH

H

δ+

δ-

δ+δ+

δ-

Chapter 4

qz

2-1 chapter 2 saturated hydrocarbons constitutional isomers iupac nomenclature conformations...

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