Question

Draw a structural formula for methyl linoleate. Make sure you show the correct configuration of groups about each carbon-carbon double bond.

Short answer

Question: Draw the structural formula of methyl linoleate and indicate the positions of cis double bonds.

Step-by-step solution

Start with the backbone of linoleic acid

Linoleic acid has a chain of 18 carbon atoms. The first carbon, called the alpha carbon, will have a carboxylic acid functional group (-COOH). The molecule has two cis double bonds, one between the 9th and 10th carbon atoms and the other between the 12th and 13th carbon atoms. Draw an 18-carbon chain with these double bonds in cis configuration and add a carboxylic acid functional group at the first carbon atom.

Add hydrogens to the single carbons

For each of the single-bonded carbons, we need to add hydrogens to satisfy the octet rule (four bonds per carbon atom). As each double-bonded carbon already has three bonds, it only needs a single hydrogen per double-bonded carbon. Go ahead and assign the remaining hydrogen atoms to the single-bonded carbon atoms.

Draw methanol

Methanol (CH_3OH) is a one-carbon alcohol with a hydroxyl group (-OH) attached to the carbon. Draw the structure of methanol, including all atoms and single bonds.

Combine the structures to form methyl linoleate

In the esterification reaction, the carboxylic acid of linoleic acid will react with the hydroxyl group of methanol. This results in the formation of the methyl ester of linoleic acid, i.e., methyl linoleate. To show the structure of methyl linoleate, simply replace the hydrogen of the hydroxyl group in methanol with the linoleic acid molecule, losing the hydroxyl group from the carboxylic acid functional group. The final structure now consists of the 18-carbon chain of linoleic acid with two cis double bonds, as described in Step 1, with a methyl group (-CH_3) replacing the hydrogen atom in the original carboxylic acid group. Congratulations! You have successfully drawn the structural formula for methyl linoleate. Make sure to clearly label the atoms and double bonds in order to clearly convey the correct configuration of groups about each carbon-carbon double bond.