Org. Chem Test 2

Front 1

Describe alkanes.

Back 1

Alkanes are hydrocarbons with single bonds ONLY. They are also the simplest and least reactive organic compounds.

Front 2

If an acyclic hydrocarbon contains N carbons, then it must contain .......... hydrogens

Back 2

2N + 2

Front 3

Straight-chain alkanes are also called ..........

Back 3

n-alkanes

Front 4

Predict the molecular formula for 4-ethyl-5,5-dimethyldodecane:

Back 4

C16H34

Front 5

Three commercial products composed primarily of alkanes

Back 5

gasoline, natural gas, jet fuel

Front 6

When one compares the densities of n-hexane and water, one finds ..........

Back 6

that n-hexane is less dense than water

Front 7

Why are alkanes described as hydrophobic?

Back 7

Because they do not dissolve well in water.

Front 8

List these in order of increasing boiling point:
n-hexane
2,3-dimethylbutane
2-methylpentane

Back 8

2,3-dimethylbutane --> 2-methylpentane --> n-hexane

Front 9

How many carbons do the primary alkane constituents of gasoline contain?

Back 9

C5H8

Front 10

Name the two major steps in refining of crude oil into usable hydrocarbon products

Back 10

1) Fractional distillation
2) Cracking

Front 11

Among butane conformers, which occur at energy minima on a graph of potential energy versus dihedral angle?

Back 11

gauche and anti

Front 12

Describe the sources of angle strain and torsional strain present in cyclopropane

Back 12

angle strain: compression of the ideal tetrahedral angle, going from 109.5 to 60.
torsional strain: occurs because of C to H bonds being eclipsed on adjacent carbons

Front 13

Describe chair conformations of trans-1,4-dimethylcyclohexane

Back 13

The higher energy chair conformation contains two axial methyl groups

Front 14

List the conformations of cyclohexane in order of increasing energy

Back 14

chair --> twist --> boat --> half-chair

Front 15

explain knocking

Back 15

causing the premature explosive combustion of certain gasoline mixtures in a car's engine

Front 16

Describe the molecules of a sample of ethane gas at room temperature

Back 16

molecules are rapidly interconverting between eclipsed and staggered conformations, but will, at any given time, have slightly higher numbers in staggered conformation

Front 17

What types of hydrocarbons are saturated?

Back 17

alkANES are saturated

Front 18

What does "mechanism of a reaction" mean?

Back 18

the complete, step-by-step description of exactly which bonds break, which bonds form, and the order in which these events occur

Front 19

chlorination of methane is characterized by a high quantum yield. Explain what this means

Back 19

many molecules of a product are formed for every photon of light which is absorbed by the reaction mixture.

Front 20

if stronger bonds are formed and weaker bonds are broken, then the reaction is ..........

Back 20

exothermic

Front 21

bond dissociation energy is the amount of energy required to break a bond ..........

Back 21

homolytically

Front 22

the major monobrominated product which results when ethylcyclohexane is subjected to free radical bromination is ..........

Back 22

a tertiary bromide

Front 23

Describe the Hammond Postulate

Back 23

related species that are similar in energy are also similar in structure

Front 24

how many distinct monochlorinated products can result when isobutane is subjected to free radical chlorination

Back 24

2

Front 25

which of the following reactive intermediates can best be described as both nucleophilic and strongly basic?

Back 25

carbanions

Front 26

In the first propogation step of the free radical chlorination of methane, which of the following occurs?

Back 26

Cl2 dissociates

Front 27

What reactive intermediate species maintains sp3 hybridization?

Back 27

methyl carbanion