Question

Draw a Lewis structure, and classify each of the following compounds. The possible classification are as follows:

alcohol, ketone, carboxylic acid, ether, aldehyde and alkene.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

Short answer

(a) aldehyde

(b) alcohol

(c) ketone

(d) ether, alkene

(e) carboxylic acid

(f) ether, alkene

(g) ketone, alkene

(h) aldehyde

(i) alcohol

Step-by-step solution

Lewis structures

All the paired and unpaired electrons must be shown while representing a Lewis structure. The paired electrons are represented as solid lines (bonds) and the unpaired electrons are represented as dots.

Functional group

A functional group may be defined as an atom or a group of atoms that gives some characteristic properties to a compound.

The compounds containing hydroxy (-OH) functional group are classified as alcohols. Alcohols have the general formula R-OH , where R= alkyl group.

The functional group is which two alkyl groups are bonded to an oxygen atom are known as ethers. Ethers have the general formula R-O-R', where R and R' represent alkyl groups.

The functional group for both aldehydes and ketones are the carbonyl group (C=O). In a ketone, there are two alkyl groups bonded to the carbonyl group whereas in an aldehyde, there is one alkyl group and one hydrogen atom bonded to the carbonyl group.

The functional group in which carboxyl group, -COOH group is present is referred to as carboxylic acid. Carboxylic acids have the general formula

R-COOH or R-CO₂H, where R= alkyl group.

Alkenes

Alkenes are the hydrocarbons containing carbon-carbon double bond (C=C) .

Identification of compounds

(a)

From the Lewis structure, it can be seen that there is one alkyl group and one hydrogen atom bonded to the carbonyl group (C=O). Therefore, this compound is an aldehyde.

(b)

From the Lewis structure, it can be seen that the compound contains hydroxy (-OH) functional group. Therefore, this compound is an alcohol.

(c)

From the Lewis structure, it can be seen that there are two alkyl groups bonded to the carbonyl group (C=O). Therefore, this compound is a ketone.

(d)

From the Lewis structure, it can be seen that there are two alkyl groups bonded to an oxygen atom. Therefore, this compound is an ether. Also, it contains carbon-carbon double bond (C=C). Hence, it can also be classified as an alkene.

(e)

From the Lewis structure, it can be seen that the compound contains carboxyl

(-COOH ) functional group. Therefore, this compound is a carboxylic acid.

(f)

From the Lewis structure, it can be seen that there are two alkyl groups bonded to an oxygen atom. Therefore, this compound is an ether. Also, it contains carbon-carbon double bond (C=C). Hence, it can also be classified as an alkene.

(g)

From the Lewis structure, it can be seen that there are two alkyl groups bonded to the carbonyl group (C=O). Therefore, this compound is a ketone. Also, it contains carbon-carbon double bond (C=C). Hence, it can also be classified as an alkene.

(h)

From the Lewis structure, it can be seen that there is one alkyl group and one hydrogen atom bonded to the carbonyl group (C=O). Therefore, this compound is an aldehyde.

(i)

From the Lewis structure, it can be seen that the compound contains hydroxy (-OH) functional group. Therefore, this compound is an alcohol.