determine whether a given reaction should be classified as an oxidation or a reduction. write an equation to represent the reduction of an aldehyde or ketone using sodium borohydride or lithium aluminum hydride. discuss the relative advantages and disadvantages of using sodium borohydride or lithium aluminum hydride to reduce aldehydes or ketones to alcohols. identify the product formed from the reduction of a given aldehyde or ketone. identify the aldehyde or ketone that should be used to produce a given alcohol in a reduction reaction. identify the best reagent to carry out the reduction of a given aldehyde or ketone. write an equation to represent the reduction of an ester or a carboxylic acid to an alcohol. identify the product formed from the reduction of a given ester or carboxylic acid. identify the esters or carboxylic acids that could be reduced to form a given alcohol.
Make certain that you can define, and use in context, the key terms below.
(organic) oxidation (organic) reduction
In your course in first‑year general occupychristmas.orgistry, you probably discussed oxidation‑reduction reactions in terms of the transfer of electrons and changes in oxidation numbers (oxidation states). In organic occupychristmas.orgistry, it is often more convenient to regard reduction as the gain of hydrogen or loss of oxygen, and oxidation as the gain of oxygen or the loss of hydrogen. There is no contradiction in using these various definitions. For example, when hydrogen is added across the double bond of ethene to reduce it to ethane, the oxidation number of the doubly bonded carbon atoms decreases from −II to −III. Similarly, when 2‑propanol
Addition of a hydride anion (H:-) to an aldehyde or ketone gives an alkoxide anion, which on protonation yields the corresponding alcohol. Aldehydes produce 1º-alcohols and ketones produce 2º-alcohols.
In metal hydrides reductions the resulting alkoxide salts are insoluble and need to be hydrolyzed (with care) before the alcohol product can be isolated. In the sodium borohydride reduction the methanol solvent system achieves this hydrolysis automatically. In the lithium aluminum hydride reduction water is usually added in a second step. The lithium, sodium, boron and aluminum end up as soluble inorganic salts at the end of either reaction. Note! LiAlH4 and NaBH4 are both capable of reducing aldehydes and ketones to the corresponding alcohol.