Question

Both 1,2 -diols and 1,3-diols can be protected by treatment with 2-methoxypropene according to the following reaction.

Short answer

Answer: The products formed when 1,2-diols react with 2-methoxypropene are ketals, while when 1,3-diols react with 2-methoxypropene, acetals are formed. These linkages protect the hydroxyl groups of the diols.

Step-by-step solution

Identify the reactants and products

In this reaction, 1,2-diols or 1,3-diols are treated with 2-methoxypropene. The 2-methoxypropene acts as a protecting agent for the diols. 1,2-diol: H(OH)C-CHR1-R2-OH 1,3-diol: H(OH)C-CHR1-CHR2-OH 2-Methoxypropene: CH2=C(CH3)OCH3

Understand the protection mechanism for diols

Protection of a diol involves conversion of hydroxyl groups (-OH) into a single group that can be removed later under specific conditions. In this case, 2-methoxypropene protects the diol by forming a ketal group (for 1,2-diols) or an acetal group (for 1,3-diols).

Reaction with 1,2-diols

When a 1,2-diol reacts with 2-methoxypropene, the two hydroxyl groups of the diol are protected by the formation of a ketal linkage. The reaction can be shown as follows: H(OH)C-CHR1-R2-OH + CH2=C(CH3)OCH3 -> HO-C(CHR1-R2-O)C(CH3)OCH3 Here, a ketal group is formed which links the two carbons of the 1,2-diol.

Reaction with 1,3-diols

When a 1,3-diol reacts with 2-methoxypropene, one of the hydroxyl groups of the diol is protected by the formation of an acetal linkage. The reaction can be shown as follows: H(OH)C-CHR1-CHR2-OH + CH2=C(CH3)OCH3 -> HO-CHR1-CHR2-O-C(CH3)OCH3 Here, an acetal group is formed that links one hydroxyl group of the 1,3-diol to the 2-methoxypropene.

Summary

In this exercise, we analyzed the reaction between 1,2-diols or 1,3-diols with 2-methoxypropene. The main focus was on understanding the protection mechanism of diols by 2-methoxypropene. The reaction for 1,2-diols involves the formation of a ketal linkage, while the reaction for 1,3-diols involves the formation of an acetal linkage.