Chapter 4: Alkanes

Question 1

[4.1] What is the molecular formula of acyclic alkanes?

Answer 1

CnH2n+2

Question 2

[4.1] What is the molecular formula of cyclic alkanes?

Answer 2

CnH2n

Question 3

[4.1] This type of isomer differs in the way the atoms are connected to each other

Answer 3

constitutional isomers

Question 4

[4.1] What do you call a CH2 group

Answer 4

methylene

Question 5

[4.1] a group of compounds that differ by only a CH2 group is called a?

Answer 5

homologous series

Question 6

[4.2] Prefix used for naming cycloalkanes

Answer 6

cyclo-

Question 7

[4.3] What does IUPAC stand for?

Answer 7

International Union of Pure and Applied Chemistry

Question 8

[4.4] What do you create removing one hydrogen from an alkane

Answer 8

Alkyl group

Question 9

[4.8] Are alkanes water or fat soluble?

Answer 9

Fat soluble

Question 10

[4.8] In alkanes, what is the relationship of MP and BP in the number of carbons?

Answer 10

Direct

Question 11

[4.8] In alkanes, what is the relationship of BP and branching?

Answer 11

Indirect

Question 12

[4.8] In alkanes, what is the relationship of MP and symmetry?

Answer 12

Direct

Question 13

[4.9] What do you call the different arrangements of atoms that are interconverted by rotation around single bonds? What are its two types?

Answer 13

Conformations, eclipsed and staggered

Question 14

[4.9] rotating the atom on one carbon by how many degrees converts an eclipsed conformation into a staggered conformation, and vice versa?

Answer 14

60°

Question 15

[4.9] What is the angle that separates a bond on one atom from a bond on an adjacent atom

Answer 15

dihedral angle

Question 16

[4.9] What are the end-on representations for conformations, the circle representing the back carbon and the dot representing the front carbon

Answer 16

Newman projections

Question 17

[4.9] Which of the two conformations are less stable, and why?

Answer 17

Eclipsed, because of electron-electron repulsion

Question 18

[4.9] The difference in energy between the staggered and eclipsed conformations is _ kJ/mol (_ kcal/mol)?

Answer 18

12; 2.9

Question 19

[4.9] What is the energy difference between staggered and eclipsed conformations

Answer 19

Torsional energy

Question 20

[4.9] What is an increase in energy caused by eclipsing interactions; strain causes an energy increase

Answer 20

Torsional strain

Question 21

[4.9] What conformations are energy minimum and energy maximum?

Answer 21

Energy minimum - staggered conformation, most stable
Energy maximum - eclipsed conformation, least stable

Question 22

[4.10] It takes how many 60° rotations to return to the original conformation?

Answer 22

six

Question 23

[4.10] a staggered conformation with two larger groups 180° from each other

Answer 23

anti

Question 24

[4.10] a staggered conformation with two larger groups 60° from each other

Answer 24

gauche

Question 25

[4.10] an increase in energy resulting when atoms are forced too close to one another

Answer 25

steric strain

Question 26

[4.10] which is higher in energy, gauche or anti?

Answer 26

gauche

Question 27

[4.10] what is the energy difference between the lowest and highest energy conformations

Answer 27

barrier to rotation

Question 28

[4.11] What is the strain caused by an increase in energy when tetrahedral bond angles deviate from the optimum angle of 109.5°

Answer 28

angle strain

Question 29

[4.11] What is the assumption that rings with bond angles so different from the tetrahedral bond angle would be very strained an highly reactive

Answer 29

Baeyer strain theory

Question 30

[4.12] What is the most common ring size in naturally occurring compounds

Answer 30

cyclohexane

Question 31

[4.12] How does cyclohexane eliminate angle strain?

Answer 31

all C-C-C bond angles are 109.5°

Question 32

[4.12] How does cyclohexane eliminate torsional strain?

Answer 32

all hydrogens on adjacent carbon atoms are staggered, not eclipsed

Question 33

[4.12] The process by which ring bonds twist and bend in a more restricted way; conformational change

Answer 33

ring-flipping

Question 34

[4.12] What is the intermediate conformation during ring flipping?

Answer 34

Boat conformation

Question 35

[4.12] What do you call the hydrogens forced close to each other during boat conformation

Answer 35

Flagpole hydrogens

Question 36

[4.13] In a disubstituted cyclohexane, each of the two stereoisomers (cis and trans) has how many possible chair conformations?

Answer 36

two