C6H8O + NaBH4 ?

[shaquilleoneal]

Why does C6H8O + NaBH4 make C6H8OH, not C6H10O? This is question 48 of Dr. Collin's chem test 10.

 

[Verduchi]

Remember that NaBH4 is a reducing agent. A reducing agent will either gain/add: H2, H^-, or lose O,O2, or X2 where X indicates a halogen group element. In the following reaction notice 2 hydrogen atoms are now added in the final product, hence it is reduced. The problem already tells you it is a reduction RXN. Best thing to do is know your reducing and oxidizing reagents, then look at the reactions involving those reagents on the products side and ask yourself what was added or what was lost then categorize it as a reducing or oxidizing agent based on the set of rules I have listed above.

Now on the reactant side we have a ketone, remember ketones when reduced make alcohols. Do not let them trick you. Here they are trying to trick you by putting a ketone group on a cyclic compound, trying to make it harder to identify as a ketone group.

Also should be noted that the addition of: H2O, H+, or HX means that neither oxidation or reduction reaction has occurred.