Chapter 8, Problem 120AP

Draw Lewis structures for the following organic molecules: (a) methanol ${\text{ (CH}}_{\text{3}}\text{OH)}$; (b) ethanol $\left({\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}\right)$; (c) tetraethyl lead $\left[\text{Pb}{\left({\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}\right)}_{\text{4}}\right]$, which is used in “leaded gasoline"; (d) methylamine $\left({\text{CH}}_{\text{3}}{\text{NH}}_{\text{2}}\right)$, which is used in tanning; (e) mustard gas ${\text{ (ClCH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{SCH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{Cl)}$, a poisonous gas used in World War I; (f) urea $\left[{\left({\text{NH}}_{\text{2}}\right)}_{\text{2}}\text{CO}\right]$, a fertilizer; and (g) glycine ${\text{ (NH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{COOH}$), an amino acid.

Interpretation Introduction

Interpretation:

Lewisstructure for the given organic molecules are to be drawn.

Concept introduction:

The octet rule states that every element in a main group must have eight electrons in its valence shell in order to attain noble gas configuration.

Valence electrons are the electrons that are present in the last(outer) shell of an element.

Lewis dot symbols contain dotsthat provides information about valence electrons.

Lewis structures depict bonds as lines and lone pairs as dots.

Answer to Problem 120AP

Solution:

(a)

(b)

(c)

(d)

(e)

(f)

(g)

Explanation of Solution

a)Methanol (${\text{CH}}_3\text{OH}$).

There are a total 14 electrons in ${\text{CH}}_3\text{OH}$ and deduct ten electrons to account for the five bonds in the skeleton, leaving 4 electrons that can be distributed as two lone pairs on the $\text{O}$ atom.

The skeletal structure for ${\text{CH}}_3\text{OH}$ is:

The Lewis structure for ${\text{CH}}_3\text{OH}$ is:

b) Ethanol (${\text{CH}}_3{\text{CH}}_2\text{OH}$)

There are a total 20 electrons in ${\text{CH}}_3{\text{CH}}_2\text{OH}$ and deduct16electrons to account for the eight bonds in the skeleton, leaving 4 electrons to be distributed as two lone pairs on the $\text{O}$ atom.

The skeletal structure for ${\text{CH}}_3{\text{CH}}_2\text{OH}$ is:

The Lewis structure for ${\text{CH}}_3{\text{CH}}_2\text{OH}$ is:

c) Tetraethyl lead ($\text{Pb}{\left({\text{CH}}_2{\text{CH}}_3\right)}_4$), used in “leaded gasoline.”

There are a total 56 electrons in $\text{Pb}{\left({\text{CH}}_2{\text{CH}}_3\right)}_4$ and deductall fifty-six electrons to account for the 28 bonds in the Lewis structure.

The Lewis structure for $\text{Pb}{\left({\text{CH}}_2{\text{CH}}_3\right)}_4$ is:

d) Methylamine, ${\text{CH}}_3{\text{NH}}_2$, which is used in tanning.

There are a total 14 electrons in ${\text{CH}}_3{\text{NH}}_2$ and deduct12electrons to account for the six bonds in the skeleton, leaving 2 electrons to be distributed as a single lone pair on the $\text{N}$ atom.

The skeletal structure for ${\text{CH}}_3{\text{NH}}_2$ is:

The Lewis structure for ${\text{CH}}_3{\text{NH}}_2$ is:

e) Mustard gas, (${\text{ClCH}}_2{\text{CH}}_2{\text{SCH}}_2{\text{CH}}_2\text{Cl}$), a poisonous gas used in World war I.

There are a total 44 electrons in ${\text{ClCH}}_2{\text{CH}}_2{\text{SCH}}_2{\text{CH}}_2\text{Cl}$ and deduct28 electrons to account for the fourteen bonds in the skeleton, leaving 8 electrons to be distributed as three lone pairs on each $\text{Cl}$ atom and two lone pairs on the $\text{S}$ atom.

The skeletal structure for ${\text{ClCH}}_2{\text{CH}}_2{\text{SCH}}_2{\text{CH}}_2\text{Cl}$ is:

The Lewis structure for ${\text{ClCH}}_2{\text{CH}}_2{\text{SCH}}_2{\text{CH}}_2\text{Cl}$ is:

Hence, the Lewis dot structure has beendrawn.

f) Urea (${\left({\text{NH}}_2\right)}_2\text{CO}$) a fertilizer

There are a total 24 electrons in ${\left({\text{NH}}_2\right)}_2\text{CO}$ and deduct16electrons to account for the eight bonds in the skeleton, leaving 8 electrons to be distributed as one lone pair on each $\text{N}$ atom and two lone pairs on $\text{O}$ atom.

The skeletal structure for ${\left({\text{NH}}_2\right)}_2\text{CO}$ is:

The Lewis structure for ${\left({\text{NH}}_2\right)}_2\text{CO}$ is:

Given information:

g) Glycine $\left({\text{NH}}_2{\text{CH}}_2\text{COOH}\right)$, an amino acid

There are a total 30 electrons in ${\text{NH}}_2{\text{CH}}_2\text{COOH}$ and subtract 20electrons to account for the ten bonds in the skeleton, leaving 10 electrons to distribute as two lone pairs on each $\text{O}$ atom and one lone pair on the $\text{N}$ atom.

The skeletal structure for ${\text{NH}}_2{\text{CH}}_2\text{COOH}$ is:

The Lewis structure for ${\text{NH}}_2{\text{CH}}_2\text{COOH}$ is: