Chapter 4 Vocabulary

Question 1

1,3-diaxial interaction

Answer 1

Steric interactions that occur between axial substituents in a chair conformation.

Question 2

alkane

Answer 2

A hydrocarbon that lacks π bonds.

Question 3

alkyl group

Answer 3

A substituent lack- ing π bonds and comprised of only carbon and hydrogen atoms.

Question 4

Angle strain

Answer 4

The increase in energy associated with a bond angle that has deviated from the preferred angle of 109.5°

Question 5

anti conformation

Answer 5

A conformation in which the dihedral angle between two groups is 180°.

Question 6

axial position

Answer 6

For chair conforma- tions of substituted cyclohexanes, a position that is parallel to a vertical axis passing through the center of the ring.

Question 7

bicyclic

Answer 7

A structure containing two rings that are fused together.

Question 8

boat conformation

Answer 8

A conforma- tion of cyclohexane in which all bond angles are fairly close to 109.5° and many hydrogen atoms are eclipsing each other.

Question 9

bridgeheads

Answer 9

In a bicyclic system, the carbon atoms where the rings are fused together.

Question 10

chair conformation

Answer 10

The lowest energy conformation for cyclohexane, in which all bond angles are fairly close to 109.5° and all hydrogen atoms are staggered.

Question 11

Conformations

Answer 11

A three-dimensional shape that can be adopted by a compound as a result of rotation about single bonds.

Question 12

Cycloalkane

Answer 12

An alkane whose structure contains a ring.

Question 13

Cyclohexane

Answer 13

C6H12. A colourless flammable liquid cycloalkane obtained from petroleum or by hydrogenating benzene, and used as a solvent and paint remover.

Question 14

degenerate

Answer 14

Having the same energy.

Question 15

dihedral angle

Answer 15

The angle by which two groups are separated in a Newman projection.

Question 16

eclipsed conformations

Answer 16

A conformation in which groups are eclipsing each other in a Newman projection.

Question 17

equatorial position

Answer 17

For chair conformations of substituted cyclohexanes, a position that is approximately along the equator of the ring.

Question 18

flagpole interactions

Answer 18

For cyclohexane, the steric interactions that occur between the flagpole hydrogen atoms in a boat conformation.

Question 19

gauche conformation

Answer 19

A conformation that exhibits a gauche interaction.

Question 20

gauche interactions

Answer 20

The steric inter- action that results when two groups in a Newman projection are separated by a dihedral angle of 60°.

Question 21

heat of combustion

Answer 21

The heat given off during a reaction in which an alkane reacts with oxygen to produce CO2 and water.

Question 22

IUPAC

Answer 22

The International Union of Pure and Applied Chemistry. An organization that sets the rules for nomenclature (naming compounds).

Question 23

locant

Answer 23

In nomenclature, a number used to identify the location of a substituent.

Question 24

newman projections

Answer 24

A drawing style that is designed to show the conformation of a molecule.

Question 25

nomenclature

Answer 25

A system for naming organic compounds.

Question 26

norbornane

Answer 26

The common name for bicyclo[2.2.1]heptane.

Question 27

ring flip

Answer 27

A conformational change in which one chair conformation is converted into the other.

Question 28

Staggered conformations

Answer 28

A conformation in which nearby groups in a Newman projection have a dihedral angle of 60°.

Question 29

substituent

Answer 29

In nomenclature, the groups connected to the parent chain.

Question 30

torsional angle

Answer 30

The angle between two groups in a Newman projection, also called the dihedral angle.

Question 31

torsional strain

Answer 31

The difference in energy between staggered and eclipsed conforma- tions (for example, in ethane).

Question 32

twist boat

Answer 32

A conformation of cyclohexane that is lower in energy than a boat conformation but higher in energy than a chair conformation.

Question 33

Cracking

Answer 33

a process by which C−C bonds of larger alkanes are broken, producing smaller alkanes suitable for gasoline

Question 34

Reforming

Answer 34

a process in which straight-chain alkanes are converted into branched hydrocarbons and aromatic com- pounds, which exhibit less knocking during combustion.