Module 4: Saturated Hydrocarbons

Question 1

these are molecules that have different arrangements

Answer 1

conformational isomers or conformers

Question 2

these are the different arrangement s of atoms that result from bond rotation

Answer 2

conformations

Question 3

_________________ conformation is also nearly free of angle strain. It does, however, have both steric strain and torsional strain and is about 23 kJ/mol.

Answer 3

Twist-boat

Question 4

these are saturated cyclic hydrocarbons

Answer 4

cycloalkanes or alicyclic compounds (aliphatic cyclic)

Question 5

this is the repulsive interaction that occurs when atoms are forced closer together than their atomic radii allow.

Answer 5

steric strain

Question 6

it has practically no angle strain, it has a large amount of torsional strain

Answer 6

planar cyclopentane

Question 7

it has less angle strain than cyclopropane but has more torsional strain because of its larger number of ring hydrogens.

Answer 7

cyclobutane

Question 8

Increases in both boiling point and melting point as ________________ increases

Answer 8

molecular weight

Question 9

this is when energy minimum is reached at the staggered conformation where the methyl groups are 60°apart

Answer 9

gauche conformation

Question 10

the extra 12 kJ/mol of energy present in the eclipsed conformation of ethane

Answer 10

torsional strain

Question 11

These are compounds comprised of only C and H

Answer 11

hydrocarbons

Question 12

it has a total strain energy of 26 kJ/mol (6.2 kcal/mol).

Answer 12

cyclopentane

Question 13

Another effect seen in alkanes is that increased branching lowers an alkane’s ______________________.

Answer 13

boiling point

Question 14

it has considerable torsional strain because the C-H bonds on neighboring carbon atoms are eclipsed

Answer 14

cyclopropane

Question 15

The ___________________ are in the rough plane of the ring, around the ring equator

Answer 15

six equatorial positions

Question 16

this is the one in which the two methyl groups are as far apart as possible away from each other

Answer 16

anti conformation

Question 17

this twists to adopt a puckered, nonplanar conformation that strikes a balance between increased angle strain and decreased torsional strain

Answer 17

cyclopentane

Question 18

_______________________ of cyclohexane adopts a strain-free, three-dimensional shape

Answer 18

Chair conformation

Question 19

The __________________ are perpendicular to the ring, parallel to the ring axis

Answer 19

six axial positions

Question 20

these are hydrocarbons that lack π bonds

Answer 20

saturated hydrocarbons or alkanes

Question 21

this is the most strained of all rings, primarily because of the angle strain caused by its 60°C-C-C bond angles.

Answer 21

cyclopropane

Question 22

this the result of trying to force two atoms to occupy the same space.

Answer 22

steric strain