Chapter 20, Problem 9STP

(a)

Interpretation Introduction

Interpretation: The Lewis structures for each of the molecules present in ${\text{C}}_{\text{2}}{\text{H}}_{\text{6}}\text{O}$ needs to be determined.

Concept Introduction:Isomers: Are the compounds that have same molecular formula but different arrangement of atoms and properties.

Answer to Problem 9STP

  $\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{C}-\text{OH}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$ and $\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{O}-\text{C}-\text{H}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$

Explanation of Solution

The two isomers present in ${\text{C}}_{\text{2}}{\text{H}}_{\text{6}}\text{O}$ are

	Isomers	Formula	Lewis structure
1.	Ethanol	${\text{CH}}_3{\text{CH}}_2\text{OH}$	$\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{C}-\text{OH}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$
2.	Dimethyl ether	${\text{CH}}_3{\text{OCH}}_3$	$\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{O}-\text{C}-\text{H}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$

(b)

Interpretation Introduction

Interpretation: The functional group for each of the molecules needs to be labeled.

Concept Introduction : Functional group: An atom or group ofatoms in a hydrocarbonderivative that containselements in addition tocarbon and hydrogen.

Answer to Problem 9STP

  $\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{C}-\text{OH}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$ and $\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{O}-\text{C}-\text{H}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$

Explanation of Solution

Since, ethanol is an alcohol as the functional group is −OH

  $\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{C}-\text{OH}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$

And dimethyl ether is an ether group as the functional group is −O−

  $\begin{array}{l}\text{H}\text{H}\\ \left|\right|\\ \text{H}-\text{C}-\text{O}-\text{C}-\text{H}\\ \left|\right|\\ \text{H}\text{H}\\ \end{array}$

(c)

Interpretation Introduction

Interpretation: The molecules that would exhibit the stronger intermolecular forces needs to be determined.

Concept Introduction : Hydrogen bonding: Special name forunusually strong dipole−dipole attractions thatoccur among moleculesin which hydrogen isbonded to a highlyelectronegative atom(such as nitrogen,oxygen, or fluorine)

Answer to Problem 9STP

Ethanol will exhibit stronger intermolecular force than dimethyl ether.

Explanation of Solution

Since, ethanol has a hydrogen bond that is O-H bond and it is a colorless liquid that boils at $\text{78°C}$ and dimethyl ether has no hydrogen bonding.