4. Alkanes

Question 1

An aliphatic hydrocarbon having only C─C and C─H σ bonds.

Answer 1

Alkane

Question 2

A compound made up of only the elements of carbon and hydrogen.

Answer 2

Hydrocarbon

Question 3

A compound with the general formula CnH2n + 2. Also, contains the maximum number of hydrogen atoms per carbon.

Answer 3

Acyclic alkane (Saturated Hydrocarbon)

Question 4

A compound that contains carbons joined in one or more rings. Cycloalkanes with one ring have the general formula CnH2n

Answer 4

Cycloalkane

Question 5

A chemical substance used for communication in an animal or insect species.

Answer 5

Pheromone

Question 6

Two different compounds that have the same molecular formula.

Answer 6

Isomers

Question 7

Two compounds that have the same molecular formula, but differ in the way the atoms are connected to each other.

Answer 7

Constitutional isomers (Structural Isomers)

Question 8

An acyclic alkane that has all of its carbons in a row. A normal alkane is an “n-alkane” or a straight-chain alkane.

Answer 8

Normal alkane

Question 9

An acyclic alkane that has alkyl substituents bonded to the parent carbon chain.

Answer 9

Branched-chain alkane

Question 10

A CH2 group bonded to a carbon chain (─CH2─) or part of a double bond (CH2═).

Answer 10

Methylene group

Question 11

A group of compounds that differ by only a CH2 group in the chain.

Answer 11

Homologous series

Question 12

A systematic method for naming compounds developed by the International Union of Pure and Applied Chemistry.

Answer 12

IUPAC system of nomenclature

Question 13

The portion of the IUPAC name of an organic compound that indicates the number of carbons in the longest continuous chain in the molecule.

Answer 13

Parent name

Question 14

A group formed by removing one hydrogen from an alkane. Alkyl groups are named by replacing the suffix -ane of the parent alkane with -yl.

Answer 14

Alkyl group

Question 15

A group or branch attached to the longest continuous chain of carbons in an organic molecule.

Answer 15

Substituent

Question 16

The name of a molecule that was adopted prior to and therefore does not follow the IUPAC system of nomenclature.

Answer 16

Common name

Question 17

A fossil fuel containing a complex mixture of compounds, primarily hydrocarbons with 1 to 40 carbon atoms.

Answer 17

Petroleum

Question 18

The three-dimensional structure of molecules.

Answer 18

Stereochemistry

Question 19

The different arrangements of atoms that are interconverted by rotation about single bonds.

Answer 19

Conformations

Question 20

A conformation of a molecule where the bonds on one carbon are directly aligned with the bonds on the adjacent carbon.

Answer 20

Eclipsed conformation

Question 21

A conformation of a molecule in which the bonds on one carbon bisect the R─C─R bond angle on the adjacent carbon.

Answer 21

Staggered conformation

Question 22

The angle that separates a bond on one atom from a bond on an adjacent atom.

Answer 22

Dihedral angle

Question 23

An end-on representation of the conformation of a molecule. The Newman projection shows the three groups bonded to each carbon atom in a particular C–C bond, as well as the dihedral angle that separates the groups on each carbon.

Answer 23

Newman projection

Question 24

The energy difference between the staggered and eclipsed conformations of a molecule.

Answer 24

Torsional energy

Question 25

An increase in the energy of a molecule caused by eclipsing interactions between groups attached to adjacent carbon atoms.

Answer 25

Torsional strain

Question 26

An increase in energy resulting when atoms in a molecule are forced too close to one another.

Answer 26

Steric strain

Question 27

A staggered conformation in which the two larger groups on adjacent carbon atoms have a dihedral angle of 60°.

Answer 27

Gauche conformation

Question 28

A staggered conformation in which the two larger groups on adjacent carbon atoms have a dihedral angle of 180°.

Answer 28

Anti conformation

Question 29

The energy difference between the lowest and highest energy conformations of a molecule.

Answer 29

Barrier to rotation

Question 30

An increase in the energy of a molecule resulting when the bond angles of the sp3 hybridized atoms deviate from the optimum tetrahedral angle of 109.5°.

Answer 30

Angle strain

Question 31

A stable conformation adopted by cyclohexane that resembles a chair. The stability of the chair conformation results from the elimination of angle strain (all C─C─C bond angles are 109.5°) and torsional strain (all groups on adjacent carbon atoms are staggered).

Answer 31

Chair conformation of cyclohexane

Question 32

Bonds located above or below and perpendicular to the plane of the chair conformation of cyclohexane. Three axial bonds point upwards (on the up carbons) and three axial bonds point downwards (on the down carbons).

Answer 32

Axial bonds

Question 33

Bonds located in the plane of the chair conformation of cyclohexane (around the equator). Three equatorial bonds point slightly upwards (on the down carbons) and three equatorial bonds point slightly downwards (on the up carbons).

Answer 33

Equatorial bonds

Question 34

A stepwise process in which one chair conformation of cyclohexane interconverts with a second chair conformation.

Answer 34

Ring-flipping

Question 35

An unstable conformation adopted by cyclohexane that resembles a boat. The instability of the boat conformation results from torsional strain and steric strain. The boat conformation of cyclohexane is 30 kJ/mol less stable than the chair conformation.

Answer 35

Boat conformation of cyclohexane

Question 36

Hydrogens in the boat conformation of cyclohexane that are on either end of the “boat” and are forced into close proximity to each other.

Answer 36

Flagpole hydrogens

Question 37

A steric interaction between two axial substituents of the chair form of cyclohexane. Larger axial substituents create unfavorable 1,3-diaxial interactions, destabilizing a cyclohexane conformation.

Answer 37

1,3-Diaxial interaction

Question 38

Two isomers that differ only in the way the atoms are oriented in space.

Answer 38

Stereoisomers

Question 39

A process that results in a loss of electrons. For organic compounds, oxidation results in an increase in the number of C─Z bonds or a decrease in the number of C─H bonds; Z = an element more electronegative than carbon.

Answer 39

Oxidation

Question 40

A process that results in the gain of electrons. For organic compounds, reduction results in a decrease in the number of C─Z bonds or an increase in the number of C─H bonds; Z = an element more electronegative than carbon.

Answer 40

Reduction

Question 41

An oxidation–reduction reaction, in which an alkane or other organic compound reacts with oxygen to form CO2 and H2O, releasing energy.

Answer 41

Combustion

Question 42

A biomolecule with a large number of C─C and C─H σ bonds that is soluble in organic solvents and insoluble in water.

Answer 42

Lipid

Question 43

A hydrolyzable lipid consisting of an ester formed from a high-molecular-weight alcohol and a fatty acid.

Answer 43

Wax

Question 44

A class of lipids containing 20 carbons, a five-membered ring, and a CO2H group. Prostaglandins possess a wide range of biological activities.

Answer 44

Prostaglandin