Chapter 4: Nomenclature

Front 1

Cycloalkanes

Back 1

- All or some of the atoms are arranged in a ring

- general formula CnH2n+2

Front 2

Petroleum

Back 2

* Source of alkanes
* Complex mixture of organic compounds
* Mostly alkanes and aromatic compounds

Front 3

Cracking

Back 3

* Process of breaking down the molecules of larger alkanes into smaller ones
* May be accomplished with heat, or with a catalyst

Front 4

Unbranched Alkanes

Back 4

* Straightest possible arrangement
* Each carbon is bound by no more than 2 carbons

Front 5

Branched Alkanes

Back 5

Front 6

Alkane Stem Names 1-5

Back 6

meth-, eth-, prop-, but-, and pent-

Front 7

Alkane Stem Names 6-10

Back 7

hex-, hept-, oct-, non-, dec-

Front 8

Unbranched Alkyl Group Names

Back 8

Front 9

Parent Name of Alkane

Back 9

- locate the longest continuous chain of C atoms

- if 2 chains of equal length, choose chain with greater # of substituents

- Ex Hexane

Front 10

Numbering Carbons of Parent Chain

Back 10

- beginning with the end of the chain nearer the substituent

- if substituents are equidistant at both ends, choose name that gives lower number

Front 11

Substituent Group

Back 11

- Use carbon numbers of parent chain to designate location

- Give each substituent a number, listed alphabetically

- when substituents are identical, use prefix di-, tri-, tetra-

Front 12

Four Carbon Alkyl Groups

Back 12

- disregard structure defining prefixes written in italics and separated by a hyphen

Front 13

Three Carbon Alkyl Groups

Back 13

- systematic name for isopropyl is 1-methylethyl

- numbering always begins at point where group Is attached to main chain

Front 14

Neopentyl Group

Back 14

- five carbon alkyl group

Front 15

Three Carbon Alkyl Group Nomenclature Examples

Back 15

Front 16

Classification of H Atoms

Back 16

- classified based on the carbon they are attached to

Front 17

Naming Alkyl Halides (Haloalkanes)

Back 17

- if both a halo and alkyl are attached to parent chain, number from the end nearer to first substituent.

- if equal distance number carbon near alphabetical precedence

Front 18

Functional Class Nomencature

Back 18

- system for naming compounds

- uses two or more words

- final word corresponds to functional group

- preceding words describe remainder of molecule alphabetically

Front 19

Substitutive Nomenclature

Back 19

- each atom or group (substituent) is cited as a prefix or suffix to parent compound

- Only one group can be cited as suffix

- Locants (numbers) are used to tell where the group occurs

Front 20

Naming Alchohols

Back 20

- numbering of chain always begins at the end nearer the group named as suffix (OH)

- drop -e and add suffix -ol

- locant for suffix can either appear before parent name or before suffix (4-methylhexan-1-ol)

- select longest parent chain to which OH is attached

Front 21

Common Functional Class Alcohols

Back 21

Front 22

Glycol

Back 22

-AKA diol in substitutive system

- alcohols containing 2 OH groups

Front 23

Cycloalkanes

Back 23

- Alkanes in which some or all of the carbon atoms are arranged in a ring

- cyclo- added to beginning of alkane name

- Saturated cycloalkanes have the general formula CnH2n

Front 24

Naming Cycloalkanes with 1 Substituent

Back 24

- with one ring and one substituent: add name of substituent to beginning of parent name

Front 25

Naming Cycloalkanes with 2 or More Substituents

Back 25

- number carbons starting at the substituent first in alphabet, in the direction that give other substituents the lowest number

- With 3 or more substituents: begin carbon numbering at substituent that leads to the lowest locants

- Substituents are listed in name in alphabetical order

Front 26

Cycloalkylalkanes

Back 26

- When ring system is attached to a single chain with a greater number of C atoms, or when more than one ring is attached to a single chain

Front 27

Naming Bicyclic Cycloalkanes

Back 27

- contains 2 fused or bridged rings

- use name corresponding to total number of carbon atoms in rings as parent name

- add bicyclo-

Front 28

Bridge

Back 28

- Caron atoms connecting bridgeheads

Front 29

Bridgheads

Back 29

- C atoms common to both rings

Front 30

Brackets in Naming Bicycloalkanes

Back 30

- denotes number of C atoms in each bridge in order of decreasing length

Front 31

Naming Bicycloalkanes with Substituents

Back 31

- number ring system beginning at bridge head

- proceed along longest bridge to other bridgehead

- then along next longest bridge back to first bridgehead

- then shortest bridge numbered last

Front 32

Older Names for Alkenes

Back 32

Front 33

Naming Alkenes

Back 33

- select longest chain with double bond as parent chain, change ending to -ene

- number chain beginning at end closest to double bond

- designate locant for double bond as a prefix of parent name or -ene suffix

- indicate locations of substituents by numbers of carbon atoms they are attached

Front 34

Naming Substituted Cycloalkenes

Back 34

- number carbons so atoms on double bond have 1 and 2

- gives substituent the lower numbers

- do not need to specify position of double bond

Front 35

Alkenols or Cycloalkenols

Back 35

- give alcohol number the lowest number

Front 36

Vinyl Group

Back 36

- alkenyl group

- ethenyl

-C2H3

Front 37

Allyl Group

Back 37

- alkenyl group

- prop-2-en-l-yl

Front 38

cis and trans Alkenes

Back 38

- if 2 identical or substantial groups are on same side of the double bond it is cis

- if the groups are on opposite side, it is trans

Front 39

Naming Unbranched Alkynes

Back 39

- chain is numbered to give lowest numbers to triple bond carbons

Front 40

Naming Alkynol

Back 40

- OH group has priority over triple bond when numbering Carbons

Front 41

Terminal Alkynes

Back 41

- monosubstituted acetylenes

- called ehynyl group as a substituent

Front 42

Acetylenic Hydrogen Atom

Back 42

- H atom attached to 1 Carbon in a terminal alkyne

Front 43

Alkynide Ion

Back 43

- anion obtained when acetylenic H is removed

- Useful in synthesis

Front 44

Homologous Series

Back 44

- series of compounds in which each member differs from the next member by a constant unit

- members of the series are called homologues

Front 45

Unbranched Alkane Homologue Series

Back 45

- at room temperature

- C1 - C4 are gases

- C5 - C17 are liquids

- C18 and up are solids

Front 46

Boiling Points of Alkanes

Back 46

- increases with increasing molecular weight when umbranched (graph)

- due to increase in molecular surface area which increases strength of dispersion forces

- chain branching makes a molecule more compact, reducing surface area, and lowering boiling point

Front 47

Melting Points of Unbranched Alkanes

Back 47

- increases with increased molecular weight, but not as smooth as boiling point (blue)

- however is smoother when even and odd carbon chains graphed separately

- Even number carbon alkanes pack more closely in crystalline state, so they have a higher melting point

- cycloalkanes have higher melting points than open chain counterparts

Front 48

Density of Alkanes

Back 48

- alkanes and cycloalkanes are the least dense of all organic compound groups

- all densities less than 1 g/mL

Front 49

Solubility of Alkanes & Cycloalkanes

Back 49

- almost totally insoluble in water, due to very low polarity and inability to form H bonds

- liquid alkanes and cycloalkanes are soluble in one another

- dissolve in solvents of low polarity

- Good solvents: benzene, carbon tetrachloride, chloroform, and other hydrocarbons

Front 50

Conformations

Back 50

- temporary shapes that result from rotation about a single sigma bond

Front 51

Conformer

Back 51

- each individual structure of a conformation

Front 52

Conformational Analysis

Back 52

- analysis of energy changes that a molecules undergoes as its groups undergo rotation about the single bonds that join them

Front 53

Newman Projection Formula

Back 53

- means of representing the spatial relationships of groups attached to two atoms of a molecule

- take view from one atom (usually a C) directly along a selected bond axis tot eh next atom (usually a C)

Front 54

Sawhorse Formula

Back 54

- chemical formula that depicts the spatial relationships of groups in a molecule

- similar to dash wedge formula

Front 55

Staggered Conformation

Back 55

- conformation where the dihedral amgle between bonds at each of the C-C bonds is 180 degrees

- atoms or groups bonded to each end of a C-C bond are as far apart as possible

- most stable (allows for max separation of electron pairs)

- also stabilized by hyperconjugation to a lesser degree

Front 56

Dihedral Angle

Back 56

- angle between atoms or groups bonded to adjacent atoms

- when viewed as a projection down the bond between adjacent atoms

Front 57

Eclipsed Conformation

Back 57

- atoms bonded to carbons at each end of a C-C bond are directly opposed to one another

- dihedral bond angle is 0

Front 58

Hyperconjugation

Back 58

- favorable overlap between filled and unfilled sigma orbitals in the staggered conformation

- helps to stabilize staggered conformations

Front 59

Potential Energy Diagram

Back 59

Front 60

Torsional Barrier

Back 60

- barrier to rotation of groups joined by a single bond

- caused by repulsions between aligned electron pairs in the eclipsed form

- some molecules will wag back and forth with atoms in staggered or nearly staggered conformations

- molecules with more energy will rotate through an eclipsed conformation to another staggered conformation

Front 61

Torsional Barrier - Ethane

Back 61

- unless T is very low, ethane molecules will usually have enough energy to undergo bond rotation from one conformation to another
- therefore at any given moment most molecules will be in a staggered or nearly staggered configuration

Front 62

Conformational Analysis of Butane

Back 62

- barriers are larger than ethane, but still not large enough to isolate gouche and anti-conformations

- need extreme low temps to do that

Front 63

Torsional Strain

Back 63

- strain associated with an eclipsed conformation of a molecule

- caused by repulsions between the aligned electron pairs of the eclipsed bonds (Steric Hindrance)

- result of repulsive dispersion forces that cannot be relieved due to restriction of conformational mobility

Front 64

Steric Hinderance

Back 64

- repulsive interactions between electron clouds of bonded groups

Front 65

Torsional Strain - Butane

Back 65

- results from steric hindrance between terminal methyl groups and H atoms at C-2 and C-3

- also from steric hindrance directly between the 2 methyl groups

Front 66

Anti-Conformation (I)

Back 66

- does not have torsional strain

- groups are staggered

- methyl groups are 180 degrees

Front 67

Gauche Conformations

Back 67

- examples of stereoisomers

- methyl groups are close enough that dispersion forces between them are repulsive

- 60 degrees between methyl groups

- more energy than anti-conformation

Front 68

Eclipsed Conformations

Back 68

- energy maxima in potential diagram

- II and VI have repulsive dispersion forces arising from the eclipsed methyl groups and H atoms

- IV has greatest energy due to added large dispersion forces between eclipsed methyl groups

Front 69

Dispersion Forces

Back 69

- can be attractive or repulsive which depends on the distance that separates the 2 groups

- as 2 nonpolar groups are brought closer together, attraction increases to a maximum (van der waals radii)

- van der waals radii is a measure of the group's size

- as distance decreases past maximum, repulsion occurs

Front 70

Stereoisomers

Back 70

- same molecular formula and connectivity

- but different arrangements of atoms in 3D space

Front 71

Conformational Stereoisomers

Back 71

- differing in space only due to rotation about single bonds

Front 72

Stability of Cycloalkanes

Back 72

- cyclohexane is most stable cycloalkane

- difference in stability is due to ring strain

Front 73

Ring Strain

Back 73

- comprises angle strain and torsional strain

Front 74

Angle Strain

Back 74

- increase potential energy of a molecule (usually Cyclic)

- result of deviation from ideal bond angles

- caused by inherent structural constraints

Front 75

Ring Strain - Cyclopropane

Back 75

- sp3 hybridized, however bond angles are 60 degrees. Not ideal

- angle strain due to C-C sigma bonds cannot overlap as effectively as alkanes

- orbitals contain more p character

- C-C bonds are weaker, and as a result the molecule has more potential energy

- C-C bonds are considered bent

Front 76

Ring Strain - Cyclobutane

Back 76

- sp3 hybridized but has internal angles of 88 degrees

- ring is not planar but slightly folded, too much torsional strain if planer

Front 77

Ring Strain - Cyclopentane

Back 77

- sp3 hybridized, but internal angles are 108 degrees

- conformation is slightly bent, in which 1 or 2 of the atoms are out of plane

- if planer: very little angle strain but high torsional strain due to eclipsed conformation

- slight twisting of C-C atoms can occur with little change in E

- causes atoms to move into plane and causes others to move out

- makes the molecule flexible shifting rapidly from one conformation to another

- almost as stable as hexane

Front 78

Cyclohexane Conformations

Back 78

- chair conformation

- boat conformation

- twist conformation

- 99% of molecules are estimated to be in chair conformation

Front 79

Chair Conformation

Back 79

- cyclohexane

- all C-C bonds are 109.5

- free of angle and torsional strain

- bonds are staggered

- H atoms at opposite corners of the ring are maximally separated

- most stable, but more rigid than boat conformation

Front 80

Boat Conformation

Back 80

- cyclohexane

- no angle strain

- C-H bonds are eclipsed, causing torsional strain

- H atoms of C1 and C4 are close enough to cause van der waals repulsions (flagpole attractions)

- flexible

Front 81

Twist Conformation

Back 81

- flexes from boat conformation

- relieves torsional strain

- reduces flagpole interactions

- more stable than boat conformation but not chair conformation

Front 82

Conformations of Higher Cycloalkanes

Back 82

- also exist in nonplanar conformations, essentially free of angle strain

- instabilities caused by torsional strain and transannular strain

Front 83

Transannular Strain

Back 83

- Repulsive dispersion forces between H atoms across rings

Front 84

Catenanes

Back 84

- large rings threaded on chains

- large rings that are interlocked like links in a chain

Front 85

Olympiadane

Back 85

- catenane containing a linear array of 5 interlocking rings

Front 86

Axial Bonds

Back 86

- H bonds perpendicular to the average plane of the ring

- when cyclohexane is in chair conformation

- H atoms in red

Front 87

Equatorial Bonds

Back 87

- H bonds that extend from perimeter of ring

- when cyclohexane is in chair conformation

- H atoms in black

- alternate from slightly up to slightly down in their orientation from one carbon to the next

Front 88

Chair-Chair Ring Flip

Back 88

- change in cyclohexane ring converting one chair conformation to another

- axial bonds become equatorial and vice versa

Front 89

Drawing Chair Conformational Structures

Back 89

- set of parallel lines define opposite sides of chair

- equatorial bonds are parallel to ring bonds that are one away in either direction

- if vertex of ring points up: axial points up and equatorial bond is angled slightly down

- if vertex points down: axial bond points down and equatorial bond is angles slightly upward

Front 90

Chair Conformations of Methylcyclohexane

Back 90

- interconvertable via ring flip

- in conformation I, methyl group occupies the axial position

- In conformation II, methyl groups occupies the equatorial position (most stable)

Front 91

Stability of Conformation for a Monosubstituted Cyclohexane Ring

Back 91

- most stable conformation is where substituent is equatorial

- when axial, 1,3-diaxial interactions occurs between group and axial H atoms

- generally less repulsion when any group larger than H is equatorial rather than axial

Front 92

1,3-Diaxial Interactions

Back 92

- interaction between 2 axial groups that are on adjacent C atoms

Front 93

1,3-Diaxial Interactions of tert-Butylcyclohexane

Back 93

- strain more pronounced because butyl is a larger alkyl substitute

- equatorial conformation is much more stable than axial conformation

- equatorial molecule is heavily favored at room temperature

Front 94

Stereoisomers

Back 94

- compounds with same molecular formula

- differ only in arrangement of atoms in space

- have the same connectivity, therefore are not constitutional isomers

- classified as enantiomers or diastereomers

Front 95

Cis-Tran Isomers

Back 95

- Diastereomers

- differ in stereochemistry at adjascent atoms of a double bond or on different atoms of a ring

- Cis groups are on same side of double bond or ring

- Trans are on opposite sides

Front 96

Trans 1,4-Distributed Cyclohexanes

Back 96

- two possible chair conformations

- diequatorial is the more stable conformation

Front 97

Cis 1,4-Disubstituted Cyclohexane

Back 97

- both groups are attached by an upper bond or lower bond

- exists in 2 equivalent conformations: axial-equatorial and equatorial-axial

- not equivalent if one group is larger than the other

Front 98

Non-Equivalent Cis 1,4-Disubstituted Cyclohexane

Back 98

- one group is larger than the other

- conformation with larger group equatorial will be more stable

Front 99

Trans 1,3-Disubstituted Cyclohexanes

Back 99

- one methyl group in axial position and 1 methyl group in equatorial position

- equivalent if 2 groups are the same

- non-equivalent if one group is larger, conformation where largest group is equatorial is most stable

Front 100

Cis 1,3-Disubstituted Cyclohexanes

Back 100

- 2 conformations

- one in which both methyl groups are equatorial, which is more stable

- one in which both methyl groups are axial

Front 101

Trans 1,2-Disubstituted Cyclohexanes

Back 101

- conformation in which both methyl groups are equatorial, which is more stable

- conformation in which both methyl groups are axial

Front 102

Cis 1,2-Distributed Cyclohexanes

Back 102

- 2 equivalent chair formations, equal stability

- one methyl group is axial

- one methyl group is equatorial

Front 103

Decalin

Back 103

- bicycle[4.4.0]decane

Front 104

Cis-Trans Isomerization - Decalin

Back 104

- cis-decalin 2 H atoms attached to bridgehead lie on the same side of ring

- trans-decalin H atoms are on opposite sides

- simple rotations of groups about C atoms do not interconvert

- stereoisomers with different physical properties

Front 105

Adamantane

Back 105

- tricyclic system

- contains 3D array of cyclohexane rings

- all rings are in chair form

Front 106

Chemical Reactions of Alkanes

Back 106

- C-C and H-C bonds are strong and only break at high temperatures

- C and H have nearly same electronegativity and are only slightly polarized, so they are generally unaffected by most bases

- Have no unshared electrons to offer as sites for attack by acids

- originally called paraffins (latin for little affinity)

- However react vigorously with Oxygen when appropriate mixture is ignited

- also react with Cl and Br

- react explosively with F

Front 107

Hydrogenation

Back 107

- reaction in which hydrogen adds to a double or triple bond

- accomplished through the use of a metal catalyst (platinum, palladium, rhodium, or ruthenium)

Front 108

Hydrogenation of Alkenes and Alkynes

Back 108

- Alkenes and Alkynes react with H in the presence of metal catalysts to produce alkanes

- atoms of H molecule add to each atom of the C-C double or triple bond

- alkene or alkyne is dissolved in solvent such as ethanol, add catalyst, and expose mixture to H gas under pressure

Front 109

Index of Hydrogen Deficiency

Back 109

- difference in the number of pairs of H atoms between compound under study and an acyclic alkane with the same number of carbons

- each ring or double bond provides one unit of hydrogen deficiency

Front 110

Alkadienes

Back 110

- alkenes with 2 double bonds

- General Formula CnH2n−2.

Front 111

Alkenynes

Back 111

- hydrocarbons with one double bond and one triple bond

Front 112

Alkatrienes

Back 112

- Alkenes with 3 double bonds

- CnH2n−4

Front 113

Determaining IHD

Back 113

- Each double bond consumes one molar equivalent of hydrogen and counts for one unit of hydrogen deficiency

- Each triple bond consumes two molar equivalents of hydrogen and counts for two units of hydrogen deficiency.

- Rings are not affected by hydrogenation, but each ring still counts for one unit of hydrogen deficiency

Front 114

IHD for Compounds Containing Halogen Atoms

Back 114

- count halogen atoms as though they were H atoms

Front 115

IHD for Compounds Containing Oxygen Atoms

Back 115

- ignore O atoms and calculate IHD from the remainder of the formula

- multiple structural possibilities (Ex. C4H6Cl2

Front 116

IHD for Compounds Containing Nitrogen Atoms

Back 116

- subtract one hydrogen for each N atom

- then ignore N atoms

Ex. C4H9N