Question

Write the condensed structural formula for 3 -ethyl5-methyl-3-hexanol. Is this a primary, secondary, or tertiary alcohol?

Short answer

CH3CH(C2H5)CH(OH)CH2CH(CH3)CH3; tertiary alcohol.

Step-by-step solution

Identify the main carbon chain

The main carbon chain in 3-ethyl-5-methyl-3-hexanol is hexane because the name ends with 'hexanol', indicating a six-carbon chain.

Locate the alcohol group

The suffix 'ol' in hexanol indicates the presence of a hydroxyl (-OH) group. The prefix '3-' in 3-hexanol specifies that the hydroxyl group is attached to the third carbon atom of the main chain.

Identify side groups

The name '3-ethyl-5-methyl’ indicates the presence of a two-carbon ethyl group attached to the third carbon and a one-carbon methyl group attached to the fifth carbon in the main chain.

Draw the carbon skeleton

Draw a horizontal chain of six carbon atoms (C-C-C-C-C-C) to represent the hexane backbone.

Add the substituents and functional groups

Add the ethyl group (C2H5) to the third carbon and the methyl group (CH3) to the fifth carbon, keeping the -OH group on the third carbon.

Write the condensed structural formula

With the arrangement completed, the condensed structural formula becomes: CH3CH(C2H5)CH(OH)CH2CH(CH3)CH3.

Determine the type of alcohol

Since the -OH group in 3-hexanol is attached to the third carbon, which is bonded to three other carbon atoms, it classifies as a tertiary alcohol.

Key concepts

Primary, Secondary, Tertiary Alcohols

Understanding primary, secondary, and tertiary alcohols is essential in organic chemistry. These terms describe how the hydroxyl (-OH) group in an alcohol is connected to the other carbons in the molecule. When identifying the type of alcohol:

• Primary Alcohols: The -OH group is attached to a carbon atom that is connected to only one other carbon atom. A common example is ethanol (CH3CH2OH).
• Secondary Alcohols: The -OH group is connected to a carbon that is attached to two other carbon atoms. An example is isopropanol (CH3CHOHCH3).
• Tertiary Alcohols: In this case, the -OH group attaches to a carbon bonded to three other carbons. 3-ethyl-5-methyl-3-hexanol is an example, with the -OH attached to a carbon bonded to three other carbons.

In the exercise problem, 3-ethyl-5-methyl-3-hexanol is a tertiary alcohol because the hydroxyl group resides on a carbon bonded to three adjacent carbons.

Organic Chemistry Nomenclature

Nomenclature in organic chemistry is like a system of naming to ensure each compound has a unique and descriptive name. The International Union of Pure and Applied Chemistry (IUPAC) provides guidelines for naming compounds using their structure.

• In the name 3-ethyl-5-methyl-3-hexanol, the suffix "-hexanol" tells you the main carbon chain has six carbons, and it has an alcohol group.
• The numbers preceding the substituents (3 and 5) specify the positions of ethyl and methyl groups on the carbon chain.
• The main chain number (3-) directly before "hexanol" indicates where the -OH group attaches.

Learning these rules helps decode the structure of any organic compound just by reading its name.

Functional Groups in Organic Compounds

Functional groups are specific groupings of atoms within molecules that have characteristic properties. Recognizing them is crucial for predicting the behavior of organic compounds.

• The hydroxyl group (-OH) defines alcohols and influences their properties, such as solubility in water and reactivity.
• Alkyl groups, like methyl (CH3-) and ethyl (C2H5-), are common substituents that modify the main chain, affecting the compound's boiling point and other physical properties.
• In 3-ethyl-5-methyl-3-hexanol, the alcohol functional group is a key player, making this molecule an alcohol.

Functional groups help categorize and understand organic molecules, enhancing our ability to predict their behavior in various chemical reactions.