Schaum's Outline of Organic Chemistry

George Hademenos, George Hademenos

Chapter 4 ALKANES - all with Video Answers

Educators

Chapter Questions

(a) Are the staggered and eclipsed conformations the only ones possible for ethane? (b) Indicate the preferential conformation of ethane molecules at room temperature. (c) What conformational changes occur as the temperature rises? $(d)$ is the rotation about the $\sigma \mathrm{C}-\mathrm{C}$ bond, as in ethane, really "free"?

Narayan Hari

Numerade Educator

05:45

Problem 4

How many distinct compounds do the following structural formulas represent?
(Figure can't copy)

Bin Chen

Numerade Educator

01:49

Problem 5

(a) Which of the following compounds can exist in different conformations? (1) hydrogen peroxide, $\mathrm{HOOH}$; (2) ammonia, $\mathrm{NH}_3$; (3) hydroxylamine, $\mathrm{H}_2 \mathrm{NOH}$; (4) methyl alcohol, $\mathrm{H}_3 \mathrm{COH}$. (b) Draw two structural formulas for each compound in $(a)$ possessing conformations.

Adriano Chikande

Numerade Educator

01:06

Problem 6

Explain the fact that the calculated entropy for ethane is much greater than the experimentally determined value.

Adriano Chikande

Numerade Educator

Problem 7

Give two factors that account for the resistance to rotation through the high-energy ectipsed conformation.

Check back soon!

02:01

Problem 8

How does the relative population of an eclipsed and a staggered conformation depend on the energy difference between them?

Danielle Aguilar

Numerade Educator

View

Problem 9

Draw a graph of potential energy plotted against angle of rotation for conformations of $(a) 2,3$ dimethylbutane, (b) 2-methylbutane. Point out the factors responsible for energy differences.

Lottie Adams

Numerade Educator

01:54

Problem 10

Name the alkyl groups originating from $(a)$ propane, $(b) n$-butane, $(c)$ isobutane.

Sima Sarker

Numerade Educator

00:17

Problem 11

Use numbers $1,2,3$, and 4 to desigante the $1^{\circ}, 2^{\circ}, 3^{\circ}$, and $4^{\circ} \mathrm{C}^{\prime} \mathrm{s}$, respectively, in $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{C}\left(\mathrm{CH}_3\right)_2 \mathrm{CH}_2 \mathrm{CH}\left(\mathrm{CH}_3\right)_2$. Use letters $a, b, c$, etc., to indicate the different kinds of $1^{\circ}$ and $2^{\circ} \mathrm{C}^{\prime}$ s.

Heather Zimmers

Numerade Educator

02:29

Problem 12

Name by the IUPAC system the isomers of pentane derived in Problem 4.2.

Ricajoy Montero

Numerade Educator

06:11

Problem 13

Name the compound in Fig. 4-6(a) by the IUPAC system.

George Bennett

Numerade Educator

01:30

Problem 14

Write equations to show the products obtained from the reactions:
(a) 2-Bromo-2-methylpropane + magnesium in dry ether
(b) Product of $($ a $)+\mathrm{H}_2 \mathrm{O}$
(c) Product of $(a)+\mathrm{D}_2 \mathrm{O}$

Mak Smith

Numerade Educator

01:14

Problem 15

Usc I-bromo-2-methylbutane and any other one- or two-carbon compounds, if needed, to synthesize the following with good yields:
(a) 2-methylbutane
(b) 3,6-dimethyloctane
(c) 3-methylhexane

Raghvendra Singh

Numerade Educator

02:16

Problem 16

Give the different combinations of $R X$ and $R^{\prime} X$ that can be used to synthesize 3-methylpentane. Which synthesis is "best"?

Lottie Adams

Numerade Educator

02:06

Problem 17

(a) Why are alkanes inert? (b) Why do the $\mathrm{C}-\mathrm{C}$ rather than the $\mathrm{C}-\mathrm{H}$ bonds break when alkanes are pyrolyzed? $(c)$ Although combustion of alkanes is a strongly exothermic process, it does not occur at moderate temperatures, Explain.

Bhumika Jayee

Numerade Educator

03:38

Problem 18

(a) List the monobromo derivatives of (i) $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_3$ and (ii) $\left(\mathrm{CH}_3\right)_2 \mathrm{CHCH}_3$. (b) Predict the predominant isomer in each case. The order of reactivity of $\mathrm{H}$ for bromination is
$$
3^{\prime}(1600)>2 \%(82)>1(1)
$$

Timothy Gailey

Numerade Educator

01:41

Problem 19

Using the bond dissociation energies for $X_2$,
$$
\begin{array}{|l|c|c|c|c|}
\hline \mathrm{X}_2 & \mathrm{~F}_2 & \mathrm{Cl}_2 & \mathrm{Br}_2 & \mathrm{I}_2 \\
\hline \Delta H, \mathrm{~kJ} / \mathrm{mol} & +155 & +243 & +193 & +151 \\
\hline
\end{array}
$$
show that the initiation step for halogenation of alkanes.
$$
\mathrm{X}_2 \underset{\mathrm{a} \Delta}{\stackrel{\mathrm{uv}}{\longrightarrow}} 2 \mathrm{X} \text {. }
$$
is not rate-determining.

Aadit Sharma

Numerade Educator

05:20

Problem 20

Draw the reactants, transition state, and products for
$$
\mathrm{Br} \cdot+\mathrm{CH}_4 \longrightarrow \mathrm{HBr}+\mathrm{CH}_3
$$

Madeline Currie

Numerade Educator

02:24

Problem 21

Bromination of methane, like chlorination, is exothermic, but it proceeds at a slower rate under the same conditions. Explain in terms of the factors that affect the rate, assuming that the rate-controlling step is
$$
\mathrm{X}+\mathrm{CH}_4 \longrightarrow \mathrm{HX}+\mathrm{CH}_3
$$

Madeline Currie

Numerade Educator

07:25

Problem 22

2-Methylbutane has $1^{\circ}, 2^{\circ}$, and $3^{\circ} \mathrm{H}$ 's as indicated:
$$
\left(\mathrm{CH}_3\right)_2 \mathrm{CH}^{3 *} \mathrm{CH}_2 \mathrm{CH}_3
$$
(a) Use enthalpy-reaction progress diagrams for the abstraction of each kind of hydrogen by $\mathrm{X}$ (b) Summarize the relationships of relative (i) stabilities of transition states, (ii) $\Delta H^*$ values, (iii) stabilities of alkyl radicals, and (iv) rates of $\mathrm{H}$-abstraction.

Nima Gharibi

Numerade Educator

00:50

Problem 23

List and compare the differences in the properties of the transition states during chlorination and bromination that account for the differerent reactivities for $1^{\circ}, 2^{\circ}$, and $3^2 \mathrm{Hs}$.

Sam Limsuwannarot

Numerade Educator

04:30

Problem 24

Assign numbers, ranging from (1) for LOWEST to (3) for HIGHEST, to the boiling points of the following hexane isomers: 2,2-dimethylbutane, 3 -methylpentane, and $n$-hexane. Do not consult any tables for data.

Rabia Bibi

Numerade Educator

01:25

Problem 25

Write structural formulas for the five isomeric hexanes and name them by the IUPAC system.

David Collins

Numerade Educator

02:00

Problem 26

Write the structural formulas for (a) 3,4-dichloro-2,5-dimethylhexane; (b) 5-(1,2-dimethylpropyl)6-methyldodecane. (Complex branch groups are usually enclosed in parentheses.)

Vasu Makani

Numerade Educator

06:19

Problem 27

Write the structural formulas and give the IUPAC names for all monochloro derivatives of $(a)$ isopentane, $\left(\mathrm{CH}_3\right)_2 \mathrm{CHCH}_2 \mathrm{CH}_3 ;$ (b) 2,2,4-trimethylpentane, $\left(\mathrm{CH}_3\right)_3 \mathrm{CCH}_2 \mathrm{CH}\left(\mathrm{CH}_3\right)_2$.

Nicholas Sacco

Numerade Educator

02:51

Problem 28

Give topological structural formulas for $(a)$ propane, (b) butane, $(c)$ isobutane, (d) 2,2-dimethylpropane, $(e)$ 2,3-dimethylbutane, $(f)$ 3-ethylpentane, $(g)$ I-chloro-3-methylbutane, $(h)$ 2,3-dichloro-2-methylpentane, (i) 2-chloro-2,4-trimethylpentane.

Vasu Makani

Numerade Educator

04:50

Problem 29

Synthesize (a) 2-methylpentane from $\mathrm{CH}_2 \mathrm{CH}=\mathrm{CH}-\mathrm{CH}\left(\mathrm{CH}_3\right)_2,($ b $)$ isobutane from isobutyl chloride, $(c)$ 2-methyl-2-deuterobutane from 2-chloro-2-methylbutane. Show all steps.

Anupa Sharad Medhekar

Numerade Educator

03:07

Problem 30

$\mathrm{RCl}$ is treated with $\mathrm{Li}$ in ether solution to form $\mathrm{RLi}$. RLi reacts with $\mathrm{H}_2 \mathrm{O}$ to form isopentane. Using the Corey-House method, $\mathrm{RCl}$ is coupled to form 2.7-dimethyloctane. What is the structure of RCl?

Dr. Satish Ingale

Numerade Educator

01:49

Problem 31

Give steps for the following syntheses: $($ a $)$ propane to $\left(\mathrm{CH}_3\right)_2 \mathrm{CHCH}\left(\mathrm{CH}_3\right)_2$, (b) propane to 2methylpentane, $(c){ }^{14} \mathrm{CH}_3 \mathrm{Cl}$ to ${ }^{14} \mathrm{CH}_3{ }^{14} \mathrm{CH}_2^{14} \mathrm{CH}_2{ }^{14} \mathrm{CH}_3$.

Vasu Makani

Numerade Educator

02:08

Problem 32

Synthesize the following deuterated compounds: (a) $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{D}$, (b) $\mathrm{CH}_2 \mathrm{DCH}_2 \mathrm{D}$.

Ian Kaigh

Numerade Educator

00:53

Problem 33

In the dark at $150^{\circ} \mathrm{C}$, tetraethyl lead, $\mathrm{Pb}\left(\mathrm{C}_2 \mathrm{H}_5\right)_4$, catalyzes the chlorination of $\mathrm{CH}_4$. Explain in terms of the mechanism.

Catherine Lemar

Numerade Educator

01:02

Problem 34

Hydrocarbons are monochlorinated with tert-butyl hypochlorite, $t$-BuOCl.
$$
t-\mathrm{BuOCl}+\mathrm{RH} \longrightarrow \mathrm{RCl}+t-\mathrm{BuOH}
$$

Write the propagating steps for this reaction if the initiating step is
$$
t \text { - } \mathrm{BuOCl} \longrightarrow t \text {-BuO- }+\mathrm{Cl} \text {. }
$$

David Collins

Numerade Educator

02:07

Problem 35

Calculate the heat of combustion of methane at $25 \mathrm{C}$. The bond energies for $\mathrm{C}-\mathrm{H}, \mathrm{O}=\mathrm{O}, \mathrm{C}=\mathrm{O}$, and $\mathrm{O}-\mathrm{H}$ are respectively $413.0,498.3,803.3$, and $462.8 \mathrm{~kJ} / \mathrm{mol}$.

Will Li

Numerade Educator

01:22

Problem 36

(a) Deduce structural formulas and give IUPAC names for the nine isomers of $\mathrm{C}_7 \mathrm{H}_{16}$ - (b) Why is 2-ethylpentane not among the nine?

Chloe Schroeder

Numerade Educator

03:02

Problem 37

Singlet methylene, : $\mathrm{CH}_2$ (Section 3.2), may be generated from diazomethane, $\mathrm{CH}_2 \mathrm{~N}_2$; the other product is $\mathrm{N}_2$. It can insert between $\mathrm{C}-\mathrm{H}$ bonds of alkanes:
(Figure can't copy)
Determine the selectivity and reactivity of : $\mathrm{CH}_2$ from the yields of products from methylene insertion in pentane:
(Figure can't copy)
$$
\begin{array}{|l|c|c|c|}
\hline \text { Name, Kind of } \mathrm{CH} \text { insertion } & \text { Hexane, } \mathrm{CH}^{\prime} & \text { 2-Methylpentane, } \mathrm{CH}^2 & \text { 3-Methylpentane, } \mathrm{CH}^3 \\
\hline \text { Yield } & 48 \% & 35 \% & 17 \% \\
\hline
\end{array}
$$

Brittany Carnathan

Numerade Educator

05:56

Problem 38

How would the energy-conformation diagrams of ethane and propane differ?

Dr. Satish Ingale

Numerade Educator

01:19

Problem 39

1,2-Dibromoethane has a zero dipole moment, whereas ethylene glycol, $\mathrm{CH}_2 \mathrm{OHCH}_2 \mathrm{OH}$, has a measurable dipole moment. Explain.

Bobby Barnes

University of North Texas