Aldehydes and ketones can be halogenated at their α-position by reaction with Cl2, Br2, or I2, under acidic conditions. Using Br
2 under acidic conditions, an intermediate enol is formed which adds bromine at the α-position. The reaction stops after the addition of one bromine because the electron-withdrawing halogen decreases the basicity of the carbonyl oxygen, making the protonation less favorable. Draw curved arrows to show the movement of electrons in this step of the mechanism.
1 answer:
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Answer:
See explanation and images attached
Explanation:
a) In the mechanism for the acid catalysed esterification of propanoic acid using ethanol, we can see that the first step is the protonation of the acid followed by nucleophillic attack of the alcohol. Loss of water and consequent deprotonation regenerates the acid catalyst. We can see the fate of the 18O labelled ethanol in the mechanism shown.
b) In the second mechanism, an unnamed ester is hydrolysed using an acid catalyst. The attack of the acid and subsequent nucleophillic attack of water labelled with 18O leads to the incorporation of this 18O into the product acid as shown in the mechanism attached to this answer.
