Question

Draw the condensed structural formula of the organic product formed when each of the following is reduced by hydrogen in the presence of a nickel catalyst: a. ethyl propyl ketone b. formaldehyde c. 3 -chlorocyclopentanone d. 2 -pentanone

Short answer

a. CH3-CH2-CH(OH)-CH2-CH3b. CH3OHc. 3-chlorocyclopentanold. CH3-CH(OH)-CH2-CH2-CH3

Step-by-step solution

Understand the Reduction Reaction

In organic chemistry, reduction typically involves the addition of hydrogen (H2) to a molecule. When a ketone or aldehyde is reduced in the presence of a catalyst like nickel, it is converted into an alcohol.

Identify the Functional Group

Identify the carbonyl group (C=O) in each molecule. This is the part of the molecule that will be reduced to an alcohol (OH group).

Reduce Ethyl Propyl Ketone

Ethyl propyl ketone is also known as 2-pentanone. Its structure is CH3-CH2-CO-CH2-CH3. Upon reduction, the carbonyl group converts to an alcohol group, resulting in CH3-CH2-CH(OH)-CH2-CH3.

Reduce Formaldehyde

Formaldehyde is CH2O. Upon reduction, it is converted to methanol, which has the structure CH3OH.

Reduce 3-Chlorocyclopentanone

3-Chlorocyclopentanone has a structure where the carbonyl group is attached to a cyclopentane ring at position 1 and a chlorine at position 3. Upon reduction, it converts to 3-chlorocyclopentanol.

Reduce 2-Pentanone

2-Pentanone has a structure of CH3-CO-CH2-CH2-CH3. Upon reduction, the carbonyl group converts to an alcohol group, resulting in CH3-CH(OH)-CH2-CH2-CH3.

Key concepts

Reduction Reaction in Organic Chemistry

In organic chemistry, a reduction reaction involves the gain of hydrogen (H₂) or the loss of oxygen. This process is essential for converting functional groups and changing the properties of organic molecules.
When we reduce a carbonyl compound, like ketones and aldehydes, hydrogen is added to the carbon-oxygen double bond, converting it to a single bond. As a result, the carbonyl group (C=O) transforms into a hydroxyl group (OH), forming an alcohol.
This reaction generally requires a catalyst, such as nickel, to proceed efficiently.

Ketone Reduction

Ketones are organic compounds featuring a carbonyl group (C=O) bonded to two carbon atoms. To reduce a ketone:

• Add hydrogen to the carbonyl group.
• The C=O bond is broken.
• The oxygen is then bonded to one hydrogen, and the carbon to another hydrogen, forming a hydroxyl group (OH).

This process transforms the ketone into a secondary alcohol. For example, reducing 2-pentanone (CH₃-CO-CH₂-CH₂-CH₃) results in 2-pentanol (CH₃-CH(OH)-CH₂-CH₂-CH₃).

Aldehyde Reduction

Aldehydes contain a carbonyl group (C=O) at the end of a carbon chain, bonded to at least one hydrogen atom. Reduction of an aldehyde follows a similar process to ketone reduction:

• Hydrogen is added to the carbonyl carbon and the oxygen.
• The double bond in the C=O group breaks.
• The carbon forms a single bond with a hydrogen atom, and the oxygen forms a hydroxyl group (OH).

This reaction converts the aldehyde into a primary alcohol. For instance, reducing formaldehyde (CH₂O) produces methanol (CH₃OH).

Nickel Catalyst

Catalysts are substances that accelerate chemical reactions without being consumed. In carbonyl reductions, a nickel catalyst plays a crucial role:

• It provides a surface where hydrogen molecules can dissociate into individual atoms.
• These hydrogen atoms are then transferred to the carbonyl compound.
• Nickel simplifies the bond-breaking and bond-forming processes.

Using a nickel catalyst ensures the reaction is faster and more efficient, allowing the hydrogen to readily add to the carbonyl group and convert it into an alcohol.

Alcohol Formation

The end product of reducing carbonyl compounds like ketones and aldehydes is alcohol. Here's a recap:

• Reduction adds hydrogen to the carbonyl (C=O) group.
• For ketones, this forms a secondary alcohol (OH group bonded to a carbon connected to two other carbons).
• For aldehydes, the reduction forms a primary alcohol (OH group bonded to a carbon connected to one other carbon and one hydrogen).

In practical terms, understanding these reactions helps in fields like synthetic chemistry and biochemistry, where modifying molecule structures is fundamental.