Question

The compound which gives methanal, ethanal and glyoxal on ozonolysis is (a) Hexa-1,3-diene (b) Penta- 1,3 -diene (c) Penta- 1,4 -diene (d) Penta-1,2-diene

Short answer

Answer: Penta-1,4-diene

Step-by-step solution

Option (a) Hexa-1,3-diene

The structure of this compound has six carbon atoms and two double bonds at the first and third positions. If we perform ozonolysis on this compound, two double bonds will be cleaved, leading to the formation of two aldehyde groups and two ketone [O], resulting in two molecules of acetaldehyde (~(CH_3CHO~)).

Option (b) Penta-1,3-diene

The structure of this compound has five carbon atoms and two double bonds at the first and third positions. Upon performing ozonolysis, it will produce two aldehyde groups and only one ketone[O], forming one molecule of methanal(~HCHO~) and one molecule of ethanal(~CH_3CHO~).

Option (c) Penta-1,4-diene

The structure of this compound has five carbon atoms and two double bonds at the first and fourth positions. During ozonolysis, the carbon-carbon double bonds will break and form an aldehyde group and two ketone[O], producing exactly one molecule of methanal(~HCHO~), one molecule of ethanal (~CH_3CHO~), and one molecule of glyoxal (~OCHCHO~). This is the compound we are looking for.

Option (d) Penta-1,2-diene

The structure of this compound has five carbon atoms and two double bonds at the first and second positions. Performing ozonolysis on this compound will result in two carbonyl groups[O] on the first carbon atom, making it unstable and not producing the correct products. Thus, the correct answer is: (c) Penta-1,4-diene

Key concepts

Diene Analysis

Understanding diene analysis is crucial for students delving into organic chemistry, particularly in reactions like ozonolysis. A diene is an organic compound that contains two carbon-carbon double bonds. In this exercise, we analyze how different dienes react under ozonolysis to form various aldehydes. Each diene behaves uniquely because of the positioning of its double bonds.

• Hexa-1,3-diene contains six carbon atoms with double bonds between 1st and 3rd carbon.
• Penta-1,3-diene features five carbons with double bonds at the 1st and 3rd positions.
• Penta-1,4-diene has bonds between the 1st and 4th carbon, critical for producing the specific aldehyde products.

Understanding these structures helps predict what products will form post ozonolysis. Analyzing each diene's structure provides insights into the formation of methanal, ethanal, and glyoxal, crucial for confirming the correct diene.

Aldehyde Formation

Aldehyde formation is a fundamental product of ozonolysis, an oxidative cleavage reaction breaking down carbon-carbon double bonds. When ozonolysis involves dienes, the resulting molecules can include aldehydes. The position and number of double bonds determine which aldehydes form. In this exercise:

• Hexa-1,3-diene primarily yields acetaldehyde molecules due to its symmetrical structure.
• Penta-1,3-diene produces both methanal (formaldehyde) and ethanal (acetaldehyde) due to its distinct bond placements.
• Penta-1,4-diene is of special interest, creating methanal, ethanal, and the rare glyoxal, thanks to its unique bond configuration.

Understanding which aldehydes are formed requires analyzing the double bond placements and ozonolysis's bond-cleaving properties. This forms the basis for identifying which diene produces the correct mix of aldehydes.

Carbon-Carbon Double Bond

Carbon-carbon double bonds are important in organic chemistry due to their reactivity in processes like ozonolysis. These double bonds set the stage for complex reactions. In the context of this exercise, these bonds determine the resulting products when subjected to ozonolysis. Each diene studied has a unique configuration of double bonds:

• Hexa-1,3-diene features key double bonds in specific positions, dictating two molecules of acetaldehyde after reaction.
• Penta-1,3-diene has strategic double bonds that break to form methanal and ethanal.
• Penta-1,4-diene’s distinctive double bonds result in a combinations of methanal, ethanal, and glyoxal.

Recognizing these double bond patterns provides the foundation for predicting which aldehydes (or ketones in some reactions) emerge from the ozonolysis process. It’s crucial for understanding why certain compounds form post-reaction.