Q58E - Organic Chemistry (Mcmurry)

Question

As written, the following syntheses have flaws. What is wrong with

each?

Step-by-Step Solution

Answer

Answer

(a) Chlorination of toluene occurs at the ortho and para position. To synthesize the given product, first oxidize toluene to benzoic acid and then chlorinate.

(b) p-Chloronitrobenzene is inert to Friedel-Crafts alkylation because the ring is deactivated.

(c) The first two step in the sequence (mentioned on reacting arrow) are correct, but H₂/Pd reduces nitro group as well as the ketone.

Step-by-step Solution Step 1: Determine flaw in reaction (a)

(a) Chlorination of toluene occurs at the ortho and para position. To synthesize the given product, first oxidize toluene to benzoic acid and then chlorinate.

Here synthesis fails after the first step because in such given reaction, first oxidize toluene to benzoic acid and then chlorinate at the ortho and para position instead of meta position as shown as the major flaw in the synthesis of given reaction.

                                           Chlorination of toluene

Step 2: Determine flaw in reaction (b)

(b) The presence of deactivating group on the aromatic ring (such as NH₂ group) can lead to deactivation of catalyst due to the formation of complexes.

Hence, 4-chloro-3-methylaniline is inert to Friedel-Crafts alkylation because the ring is deactivated. Therefore the synthesis fails.

Step 3: Determine flaw in reaction (c)

(c) The first two step in the sequence (mentioned on reacting arrow) are correct, but H₂/Pd reduces nitro group as well as the ketone, but in the following reaction only ketone is reduced and nitro group still remains on the ring, therefore, the synthesis fails after the third step.