1. When adding the sodium borohydride solution to the vanillin solution, why are
ID: 814463 • Letter: 1
Question
1. When adding the sodium borohydride solution to the vanillin solution, why are you told to do so in a dropwise fashion?
-So you don't accidentally spill any sodium borohydride
-To prevent formation of unwanted vanillin byproducts
-to prevent formation of unwanted sodium borohydride byproducts
-Sodium borohydride is explosive
-Both A and D above are correct
(I'm leaning towards option C because that's what someone else told me but I wanted to make sure)
2. What chemical shift value on a carbon NMR would you expect to find for the carbonyl carbon in vanillin (Ar-CHO)?
*40-90 ppm
*160-185 ppm
*180-220 ppm
*150-180 ppm
*None of the above
Explanation / Answer
1. Option D is the correct answer. Sodium borohydride is explosive. It will violently react if added in one lot. Hence, it is added portionwise so that it reacts slowly.
2. Option C (180-220 ppm) is the correct answer. The aldehyde carbon atomhas chemical shift values in the region 190-200 ppm.
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