1. Which of the following will best complete the reaction below?

The answers: C and D

All of A, B, C and D can reduced the acyl chloride (C₅H₉CH₂CH₂COCl) to aldehyde (C₅H₉CH₂CH₂CHO).

However, A and B can further reduce the aldehyde (C₅H₉CH₂CH₂CHO) produced to alcohol (C₅H₉CH₂CH₂CH₂OH). Therefore, the aldehyde product will not be obtained.

In C, carbon is used to suppress the catalytic effect of Pd in the reduction reaction. Therefore, the aldehyde produced will not be further reduced and thus can be obtained.

In D, the 3 bulky O-t-But groups and the low temperature much lower the reducing power of the lithium-aluminum complex. Therefore, the aldehyde produced will not be further reduced and thus can also be obtained.

c

You need to reduce the acyl halide (easy), but stop at the aldehyde stage (more difficult). You need D. Reagent C. is too reactive unless further deactivated: see the Rosenmund Reduction.