Question

To prepare methyl ethyl ketone, which of these compounds would you oxidize: 2 -propanol, 1 -butanol, 2-butanol, or tert-butyl alcohol? Explain.

Short answer

The suitable compound to oxidize to get methyl ethyl ketone is 2-butanol.

Step-by-step solution

Structure of Methyl Ethyl Ketone

First recognize what methyl ethyl ketone is. It is a carbonyl group (C=O), with a methyl group (CH3-) on one side and an ethyl group (C2H5-) on the other side. Therefore its structure is CH3-CO-C2H5.

Identify the Suitable Compound

Oxidation of a secondary alcohol produces a ketone. So we need to find which of the given alcohols is secondary and would produce methyl ethyl ketone when oxidized. Looking at the given compounds: 2-propanol, 1-butanol, 2-butanol, and tert-butyl alcohol, only 2-butanol has the required structure. Upon oxidation, 2-butanol can yield a ketone with a carbonyl group connected to a methyl group on one side and an ethyl group on the other side, which is methyl ethyl ketone.

Explanation

2-Propanol and tert-butyl alcohol are not secondary alcohols, so they cannot form a ketone. 1-Butanol is a primary alcohol and upon oxidation, will yield a carboxylic acid, not a ketone. Thus, 2-butanol is the right compound to oxidize.

Key concepts

Oxidation of Alcohols

Understanding the oxidation of alcohols is critical when delving into organic chemistry, particularly when synthesizing compounds such as methyl ethyl ketone. Oxidation, in this context, refers to a chemical reaction where an alcohol loses electrons and increases its oxidation state.

In these reactions, an oxidizing agent is required to facilitate the electron removal. Depending on the type of alcohol—primary, secondary, or tertiary—the oxidation product varies. Primary alcohols can be oxidized to form aldehydes, which can be further oxidized to carboxylic acids. Secondary alcohols, such as 2-butanol, typically get oxidized to form ketones. Tertiary alcohols, like tert-butyl alcohol, resist oxidation under mild conditions because they lack a hydrogen atom on the carbon with the hydroxyl group.

Secondary Alcohols

Secondary alcohols lie at the heart of many synthesis problems in organic chemistry. They are characterized by the presence of a hydroxyl group (-OH) attached to a carbon atom that is itself connected to two other carbon atoms. This structure is distinct from primary alcohols, where the hydroxyl-containing carbon is only connected to one other carbon, and from tertiary alcohols, where it's connected to three.

When it comes to the synthesis of methyl ethyl ketone, a secondary alcohol like 2-butanol is the required starting material. This is because the oxidation of a secondary alcohol leads specifically to the formation of a ketone, where the carbonyl carbon is flanked by two other carbon atoms. In choosing 2-butanol, you're targeting the correct carbon structure to achieve the desired methyl and ethyl groups on either side of the carbonyl once oxidized.

Organic Chemistry Reactions

Organic chemistry is ripe with vast types of reactions, each with unique reagents, conditions, and outcomes. Synthesizing a compound like methyl ethyl ketone involves understanding and executing a particular type of reaction: alcohol oxidation. This reaction is just one example of the many transformations that organic molecules can undergo.

Recognizing functional groups and predicting reaction outcomes are foundational skills in organic chemistry. In the case of the exercise, selecting the right starting alcohol for oxidation hinges on knowing that secondary alcohols yield ketones. With practice, chemists develop intuition for the behavior of molecules and can design pathways to synthesize complex structures, highlighting the diversity and excitement found in studying organic chemistry reactions.