4. Alkanes

Question 1

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

Answer 1

Alkanes

Question 2

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

Answer 2

Hydrocarbons

Question 3

A compound with the general formula CnH2n + 2. They contain the maximum number of hydrogen atoms per carbon.

Answer 3

Acyclic Alkane (Saturated Hydrocarbons)

Question 4

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

Answer 4

Cycloalkane

Question 5

Two different compounds that have the same molecular formula.

Answer 5

Isomers

Question 6

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

Answer 6

Constitutional Isomers (Constitutional Isomer)

Question 7

An acyclic alkane that has all of its carbons in a row.

Answer 7

Straight-Chain Alkane (Normal Alkane)

Question 8

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

Answer 8

Branched-Chain Alkane

Question 9

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

Answer 9

Methylene Group

Question 10

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

Answer 10

Homologous Series

Question 11

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

Answer 11

IUPAC System of Nomenclature

Question 12

The name of a molecule indicating the compound’s chemical structure. The systematic name is also called the IUPAC name.

Answer 12

Systematic Name

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

If the number of the carbons in the ring is greater than/equal to the number of carbons in the longest chain.

Answer 16

Naming a compound as a Cycloalkane

Question 17

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

Answer 17

Common Names

Question 18

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

Answer 18

Petroleum

Question 19

The three-dimensional structure of molecules.

Answer 19

Stereochemistry

Question 20

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

Answer 20

Conformations

Question 21

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

Answer 21

Eclipsed Conformation

Question 22

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

Answer 22

Staggered Conformation

Question 23

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

Answer 23

Dihedral Angle

Question 24

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 24

Newman Projection

Question 25

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

Answer 25

Torsional Energy

Question 26

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

Answer 26

Torsional Strain

Question 27

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

Answer 27

Steric Strain

Question 28

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

Answer 28

Barrier to Rotation

Question 29

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 29

Angle Strain

Question 30

A stable conformation adopted by cyclohexane that resembles a chair that 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 30

Chair Conformation of Cyclohexane

Question 31

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 31

Axial Bonds

Question 32

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 32

Equitorial Bonds

Question 33

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

Answer 33

Ring-Flipping

Question 34

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 34

Boat Conformation of Cyclohexane

Question 35

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 35

Flagpole Hydrogens

Question 36

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 36

1,3-Diaxial Interaction

Question 37

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

Answer 37

Stereoisomers

Question 38

An isomer of a ring or double bond that has two groups on the same side of the ring or double bond.

Answer 38

Cisisomer

Question 39

An isomer of a ring or double bond that has two groups on opposite sides of the ring or double bond.

Answer 39

Transisomer

Question 40

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 40

Oxidation

Question 41

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 41

Reduction

Question 42

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

Answer 42

Combustion

Question 43

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 43

Lipids