Question

Explain the following observation in a concise manner. Use equations, mechanisms, diagrams and/or resonance structures to illustrate your answer. In a mixture containing the molecules A and B, the labelled methyl groups appear at 8 1.5 and 8-4.2 ppm. Indicate which molecule gives rise to the upfield methyl shift and which molecule gives the more downfield signal Justify your prediction 16 marks Each of the following syntheses will not produce the desired product. In each case, identify the flaw in the synthesis. 1. Bra, FeBry 2. AICI CI 1. HNO3, H2SO4 2. ETCI, AICI: [2 x 1% marks] e. A synthesis of compound C is outlined below. Starting with benzene, provide appropriate reagents and conditions for steps i. to vii. that will bring about the transformations as shown. OLQ- 17 marks) 1....6

Answer 1

1) When the aromatic moiety is placed in a magnetic field, then pi electrons in it are induced to circulate around, which produces a new magnetic field which is called as an anisotropic one. Due to this effect, protons above the ring will be shielded. This effect is observed in Molecule A, in which CH3 group is placed in an anisotropic field which causes up field shift of the CH3 protons.

Brz, FeBrz para product is observed instead of meta product as shown in the question AICI: 1-(4-bromophenyl)propan-1-one Due to electron highly withdrawing nature of nitro, ring does not undergo friedel craft acylation reaction e) co CuCN COOH COOME methanol, SOCI H2O/H, heat