Sample exam 3 org 2 07

Sample exam 3 org 2 07 - Organic Chemistry 2 CHMU313...

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Unformatted text preview: Organic Chemistry 2 CHMU313 Midterm Exam 4/10/07 Name Questions 1-17, 5 points each. For multiple choice questions, place the capital letter corresponding to the correct answer on the line at the left of each question. 1. Which is a correct name for: a A) 2-methylpyrazine B) 2-methylpiperidine N CH C) 2-methyloxacyclohexane D) 2—methylpyrrolidine H 3 E) 2—methylpyridine 2. Which is a correct name for: /CH3 A) N-methyloxetane B) N—methyloxacyclobutane N C) N—methylazacyclobutane D) 1-methylaziridine D E) l-methylbutanamine 3. Which is a correct name for : CH3CH2NCH2CH2CHZCH3 A) N-ethyl—Z-pentanamine B) butylethylmethylamine. (EH ’ C) N—ethyl—N—methylpentamine D) N—methylethylbutanannne 3 E) 3-methy1—3-heptanamine 4. For compounds A-D below, which is least acidic? / + H + + I \ + @133 ©NH3 < N: t“ 0‘ N, (H l B H H H C 5. For compounds A—D below, which is most acidic? A H N if N _\\+, / \ / N_H " / \ / \ <_, If a; q A ‘ B H C II} D lil _ 6. Imidazole has a pKa for its conjugate acid (imidazolium ion) of 6.8. The pKa for imidazole itself is 14.4. At a pH of 7.2, which of the following statements is true? A) The major form present is the imidazolium ion. B) The major form present is imidazole itself. C) The major form present is the imidazole anion. D) The imidazolium ion and imidazole are present in a 1:1 ratio. E) The imidazole anion and imidazole are present in a 1:1 ratio. “.3. .— 7. Which of the following is not true about carbohydrate A? A H\C¢O A) A is a pentose HO H B) A is an L-sugar H OH C) A is a monosaccharide H0 H D) A can form a pyranose ring CHZOH E) A is a nonreducing sugar 8. Which of the following is true about D-mannose‘? A) D—mannose is a ketose B) D—mannose is an enantiomer of D—glucose C) D—mannose forms the same osazone as D-fi'uctose D) D-mannose is a heptose E) D-mannose is a diastereomer of D-fiuctose 9. How many open-chain stereoisomers are possible for a 2-ketopentose? A) 2 B) 4 C) 6 D) 8 E) 16 10. What is the correct Haworth projection of the pyranose form of B-D-allose? H O CHZOH CHZOH CH20H \c’ A 0 B OH 0 C OH OH H OH H OH OH OH OH H OH OH OH OH 0H 0H OH H OH CHZOH OH CHZOH CH20H D O E 0H 0 OH OH 0 D-allose OH OH OH 11. A Haworth projection of one of the cyclic forms of D-galactose is shown below. Which is the corresponding chair conformation? CHZOH 0H 0H 0 A CHZOH B OH HO 0 HO CHZOH H0 0 OH O OH OH 0 D—gahctose OH OH OH C HO CH30HO n CHZOH E CH2OH HO HO O O OH 0 OH 0 HO 0 OH ,3, 12. At pH 5, which represents the predominant form of histidine in solution? (pKa values for histidine are 9.17, 6.04, and 1.82) H N KIH is” 13H N /1 €ng 0' CIP13 0‘ (if3 OH [N CH? T 3" CH2’ T m CHz’ ‘n/ H A 0 H B O H H C 0 H H + \ + \ + + /N )11H3 N 11le N ITIH3 <16 l /CH OH | /CH 0‘ /CH OH I CH2 Tr I CH2 T I CH2 T H D O H E O H F 0 13. What is the pI value for histidine? A) 3.93 B) 5.50 C) 5.68 D) 6.04 E) 7.60 14. Which of the following amino acids has the highest pI value? (all shown at pH 1) H3§CH2CHZCH20HZCHCOZH CHssCH2CH2CIHC02H H02CCH2CH2$HC02H 4.111143 +NH3 , +NH3 A lysine B methionine C ghnarmcamd + CHZCHCOZH H3NCH2C02H l +NH3 1) glycine E phenylalanine 15. Which amino acid would be eluted first, at pH 4, from a cation exchange column, packed with a cation-exchange resin such as Dowex 50? (see problems 12 and 14 for structures) A) glycine B) phenylalanine C) lysine D) glutamic acid E) histidine 16. For D—glucose, write the Haworth projection of the B-filranose form. .. Ll , _______ 17. Which of the 5 heptapeptides A—E below could be the primary structure of a heptapeptide for which the following observations were made: (note that amino acid sequences are written left to right, starting with the N—terminal amino acid) i) Complete hydrolysis showed 2 Val, 2 Ala, Glu, Ser, Arg ii) Edman’s reagent released Glu iii) A carboxypeptidase released Ala iv) In addition to individual amino acids, partial hydrolysis gave three peptide fragments with the sequences: Val-Ser—Ala, Glu-Val, and Val-Arg A) Glu—Val—Arg—Ala—Val-Ser-Ala B) Ala-Ser-Val-Ala-Arg-Val-Glu C) Ala-Val-Ser-Ala—Val—Arg—Glu D) Glu-Val-Ser-Ala—Glu-Val—Arg E) Val—Ser—Ala—Glu—Val—Arg—Ala 18. (8 points) Are there any other heptapeptides that would satisfy the information given in Problem 17 ? If so, what are they? 19. (8 points) a) Write out the entire structure, as it would exist at pH 7, of glycine—lysine-methionine (Gly~Lys—Met), showing a line for each bond (i.e., C—C, C—N, C=O, N—H, etc.). Don’t bother to try to show conformation of the structure, and refer to problem 15 for amino acid structures. b) Would the p1 value for this tripeptide most closely match the p1 of glycine, or lysine, or methionine? Explain briefly. ._ 5‘ _. 20. (9 points) Write the mechanism for the reaction of pyrrole with acetic anhydride. Explain the preference for reaction at the 2-po sition rather than the 3-positi0n. H H H H H H ...
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This test prep was uploaded on 04/21/2008 for the course CHEM 313 taught by Professor Forsyth during the Spring '08 term at Northeastern.

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Sample exam 3 org 2 07 - Organic Chemistry 2 CHMU313...

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