Which of the following, will provide a meta, nitro (NO2) compound, upon nitration with HNO3/H2SO4?

Question

BlackTom AI · Accepted Answer

To determine which substrate will give a meta-nitro product upon nitration with a mixture of HNO3/H2SO4, we need to identify the directing effect of the substituent already present on the benzene ring.

Option a: The substrate shows a formyl group (CHO) attached directly to the benzene ring. The formyl group is a strong electron-withdrawing group and is a meta-director in electrophilic aromatic nitration. Therefore, nitration is expected to yield the meta-nitrobenzaldehyde predominantly. This option correctly predicts a meta relationship between NO2 and CHO.

Option b: The structure appears to be a methoxy group (–OCH3) attached to the ring. The methoxy group is an electron-donating group and directs electrophilic nitration to the ortho and para positions relative to itself. Thus, nitration would not give the meta product, making this choice incorrect for meta selectivity.

Option c: A bromine substituent on the ring is an unusual case: halogens are deactivating but ortho/para-directing due to resonance donation, though their deactivating nature leads to slower reaction. The directing effect is still toward the ortho/para positions, not meta, so this would not yield a meta-nitro product.

Option d: The hydroxyl group (–OH) is a strongly activating, ortho/para-director. Nitration would predominantly occur at the ortho and para positions relative to the OH group, not meta. Therefore, this option is not correct for meta nitration.

Option e: A methyl group (–CH3) is an electron-donating, ortho/para-director. Nitration would occur mainly at the ortho and para positions, not meta, so this option does not provide a meta product.

In summary, only the substrate bearing the formyl group (CHO) directly on the ring (option a) directs nitration to the meta position, producing meta-nitrobenzaldehyde as the major product.

Which of the following, will provide a meta, nitro (NO2) compound, upon nitration with HNO3/H2SO4?单项选择题

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