1. An unknown has a positive reaction in the 2,4-Dinitrophenylhydrazine test and

Question

1. An unknown has a positive reaction in the 2,4-Dinitrophenylhydrazine test and a negative reaction to the chromic acid test. The unknown is a ketone.

a.True

b. False

2. An unknown is believed to be an aldehyde. This is confirmed by looking for a signal at ____ ppm in the proton NMR.

a. 7 to 8

b. 10 to 12

c. 1 to 2

d. 9 to 10

3. A ketone and an aldehyde are indistinguishable using IR.

a. True

b. False

4. An unknown with a positive reaction for the acetyl chloride and chromic acid test, is a ________ .

a. tertiary alchol

b. primary alcohol

c. secondary alcohol

5. An unknown has a strong stretch in the IR in the region between 1725 and 1700 cm-1 and a broad absorption between 3400 and 2400 cm-1. This unknown will have an acidic pH.

a. True

b. False

Explanation / Answer

1) True; Ketones give +ve test with 2,4-DNP and they doesn't undergo oxidation with chromic acid (test negative).

2) d. 9 to 10 (aldehydic hydrogen in H-NMR seen between 9 - 10 ppm)

3) False (aldehyde give characteristic C-H stretching of 2690-2840(2 bands) and it is not observed with ketone)

4) b. primary alcohol (tertiary alcohol doesn't give positive chromic acid test)

5) a. True (IR stretching indicates compound is having -COOH functionality, which is an acid)

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