Question

CHEM 242 Score (100): TEST #3 July 24, 2014 (Thursday) NAME PART A. (3pt each) Please circle the right answer. Where would be the absorption peak of a carbonyl, C-O, stretching in IR? a) at 3300 cm b) at 2980 cm cat 1700 crm d) at 1200 cm 2. Which one is the most reactive with a Grignard reagent in nucleophilic addition rxn? a) Acetone b) benzaldehyde c)Butanone d) acetophenone 3. What is the purpose of protonating a carbonyl? a) It makes the carbonyl carbon more electrophilic. b) It makes the carbonyl carbon more nuclcophilic. c) It converts a carbonyl group into a carboxylic acid. d) It makes the oxygen on the carbonyl having more negative charge 4. The 'H NMR chemical shift of hydrogen atom in a aldehyde group, -CHO, would be at a) 1.0-2.0 ppm ) 2.0-3.0 ppm c) 5.0-6.0 ppm d9.0-10.0 ppm 5. Which of the following is a secondary amine? a) cyclohexylamine c) pyrrole b) 3-aminopentane d) N,N-dimethylaniline 6. What kind of charge would be found at the carbonyl carbon? a) It is a partial negative charge. c) It never has a charge b) It is a partial positive charge d) It is depends upon the solvent. 7. In the acid-catalyzed reaction of acetone with an alcohol, what is the intermediate? a) Acetal b) Hemiacetal c) alcohol d) aldehyde 8. Which one would give aldehyde, when it reacts with a primary alcohol? a) Grignard b) PCC c)LiAIH d) Hg(OAc2 with water, then NaBH 9. Wolff-Kishner reduction on cyclohexanone gives a) cyclohexene b) cyclohexane c) benzene d) gem-diol 10. Which of the following amines has the lowest pKb? a) Triethyl amine b) aniline c) p-nitro aniline d) piperidine 11. The number of a-hydrogen in the pentanal is 12. Chloroacetic acid is more acidic than acetic acid. Why? a) Chlorine in chloroacetic acid will stabilize its conjugate base by pulling electrons b) Chlorine in chloroacetic acid will destablize its conjugate base by pulling electrons. c) Chlorine in chloroacetic acid will stabilize its conjugate acid by pulling electrons. d) Chlorine in chloroacetic acid will destabilize its conjugate acid by pulling electrons. Page total:

Answer 1

CHEM 242 Score (100) TEST #3 July 24, 2014 (Thursday NAME: PART A. (3pt each) Please cirele the right answer 1. Where would be the absorption peak of a caronyl, C-O, stretching in IR? a) at 3300 cm b) at 2980 cm at 1700 cnm d) at 1200 cm 2. Which one is the most reactive with a Grignard reagent in nucleophilic addition rxn? Acetone b) benzaldehyde c) Butanone d) acetophenone is the purpose of protonating a carbonyl? It makes the carbonyl carbon more electrophilic. b) It makes the carbonyl carbon more nucleophilic. c) It converts a carbonyl group into a carboxylic acid. d) It makes the oxygen on the carbonyl having more negative charge 4. The 'H NMR chemical shift of hydrogen atom in a aldehyde group, CHO, would be at a) 1.0-2.0 ppm 6)2.0-3.0 ppm c)5.0-6.0 ppm .0-10.0 ppm н example 5. Which of the following is a secondary amine? a cyclohexylamine an amine that has NH group is called the secondary amine group. b) 3-aminopentane d) N,N-dimethylaniline pyrrolc pyrrole 6. What kind of charge would be found at the carbonyl carbon? a) It is a partial negative charge c) It never has a charge It is a partial positive charge d) It is depends upon the solvent 7. In the acid-catalyzed faction of acetone with an alcohol, what is the intermediate? a) Acetal Hemiacctal c) alcohol d) aldehyde 8. Which one woyld give aldehyde, when it reacts with a primary alcohol? a) Grignard PCC LAH d)Hg(OAc)2 with water, then NaBH 9. Wolff-Kishner reductien on cyclohexanone gives a) cyclohexene c) benzene d) gem-diol 10. Which of the following amines has the a) Triethyl amine b) aniline p-nitro aniline d) piperidine 11. The number fa-hydrogen in the pentanal is ОНС 12. Chloroacetic acid is more acidic than acetic acid. Why? chlorine in chloroacetic acid will stabilize its conjugate base by pulling electrons. b) Chlorine in chloroacetic acid will destablize its conjugate base by pulling electrons c) Chlorine in chloroacetic acid will stabilize its conjugate acid by pulling electrons d) Chlorine in chloroacetic acid will destabilize its conjugate acid by pulling electrons. Page total