GRE Subject Test: Chemistry : Aldehyde Chemistry
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Example Questions
Example Question #3 : Reaction Types
Acetaldehyde 
oxidized . . . carboxylic acid
oxidized . . . amide
reduced . . . alkane
reduced . . . alcohol
reduced . . . alkane
The correct answer is that the aldehyde is reduced to an alkane. In viewing the final product, we see that acetaldehyde would be reduced to ethane. The reaction of any aldehyde or ketone with hydrazine and the subsequent addition of base and heat will result in that aldehyde or ketone being reduced to an alkane, and is referred to as the Wolf-Kishner reaction. The Wolf-Kishner reagent is a commonly tested reducing agent.
Example Question #1 : Help With Grignard Reactions
What reagent(s) will successfully complete the synthesis reaction shown above?
N-propyl-MgBr; hydronium ions
Isopropyl-MgBr; hydronium ions
Ethyl-MgI; hydronium ions
Methyl-MgCl; hydronium ions
N-propyl-MgBr; hydronium ions
This is an example of a Grignard reagent reaction. Because we are adding three carbons to our chain, the Grignard reagent we need must have three carbons on it. We can therefore rule out methyl grignard and ethyl grignard.
N-propyl is the straight-chained 3-carbon alkane, while isopropyl is branched. Looking at our final product, we can see the carbon chain we have added is straight-chained, and thus N-propyl Grignard is the best option. Because Grignard reagents are relatively basic, we must add an hydronium ion workup to protonate our alcohol.
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