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Chemistry 251/253

Homework 12 Answer Key

1) O=C(NCc1ccccc1)c2ccccc2

2. CCOC(=O)c1ccc(C)cc1

3. CC(C)OC(=O)Nc1ccccc1

4. CC(C)c1ccc(Cc2ccc(cc2)C(C)C)cc1

5. CCOc1ccc(cc1)C(C)(C)c2ccc(OCC)cc2 This reaction parallels the one presented in Figure 5 of the topic Biopolymers I .

6. CCNCc1ccccc1

7.CC(=O)NCC(=O)OCc1ccccc1

8CCNC(=O)Nc1ccccc1C

9. Glycolysis, the breakdown of D-glucose into acetic acid, begins with this isomerization: Draw the structure of the likely intermediate in this reaction

OCC(O)C(O)C(O)C(=CO)O The reaction involves keto-enol tautomerization. The likely intermediate is the enol form of D-glucose.

10.* Another step in glycolysis involves the following reaction:

Draw the structure of compound A. OC[C@@H](O)C=O

11.* Draw the structure of glycylalanine.C[C@H](NC(=O)CN)C(=O)O

12. Assume you had a basic solution which contained the amino acid arginine in the following form:As you begin to acidify the solution, which atom will be protonated first? Enter the number of the atom in the appropriate text field. 5 Protonation of this nitrogen produces a cation that is resonance stabilized.

13. Which atom would be protonated second? 2

14. Mutations in DNA may result from changes in the structure of one of the heterocyclic bases attached to the backbone of the nucelic acid. One such mutation involves the hydrolytic deamination of cytosine. Draw the product of the hydrolytic deamination of the the cytosine analog shown in the following reaction:

 

Cn1ccc(=O)nc1O or Cn1ccc(O)nc1=O or Cn1ccc(=O)[nH]c1=O I accepted different tautomeric forms of this structure.

15. Draw the structure of the DNA fragment that is complementary to.

Nc1nc2n(cnc2c(=O)[nH]1)C3CC(OP(=O)([O-])[O-])C(OP(=O)([O-])[O-])O3

16. The amino acid histidine, , is found at the active site of many enzymes, where it functions as a base in the transfer of a proton from a substrate. Which of the nitrogen atoms in histidine is the proton transferred to? Enter the number in the text field. 3 The lone pair of electrons on N-2 is part of the aromatic pi system. The lone pair on N-3 is not. It is perpendicular to the pi system.

17. Of the 19 L-amino acids, 18 have the S configuration at the a-carbon. What is the name of the amino acid that has the R configuration? Enter just the name, e.g. glycine. Do not enter any stereochemical designation. Watch your spelling.

CYSTEINE or CYSTINE

18.

COC(=O)C(C)NC(=Nc1ccccc1)S or COC(=O)C(C)NC(=S)Nc1ccccc1

19. How many of the following compounds qualify as monoterpenes? 1 or 0 The first choice is the only one that contains 10 carbons, but they two 5-carbon fragments are not connected in a head-to-tail manner, so I accepted either 0 or 1 as correct.

 

20. A monoterpene with the molecular formula C10H18 did not decolorize a 2% solution of Br2/CCl4. The 13C-NMR spectrum of this material showed 7 peaks, all in the 19-50 ppm range. Draw a structure that is consistent with this data.

CC1(C)C2CCC1(C)CC2 or CC1(CCCC2CCC1)C2

21. In the following reaction, compound Bhas the molecular formula C10H11D. Draw the structure of this compound.[2H]C(=C(C)c1ccccc1)C

22.COCc1ccccc1

23. The following reaction produces a mixture of products with the molecular formula C12H13Br. Draw the structure of the compound that should be formed in the greatest amount.

CC1=CC(C)(Br)Cc2ccccc12 A Br atom will abstract a tertiary hydrogen preferentially.

24.CC1CCCC(C)(O)O1

25*. Deduce the structure of compound C:CC(C)(C)/C(=C\c1ccccc1)/c2ccccc2

26. Enter the number of the compound that would undergo dehydrobromination faster when treated with an ethanolic solution of KOH: 2 The elimination requires the molecules to adopt the other chair conformation so that the dihedral angle between the H and Br atoms is 180 degrees. In compound 1, this forces the t-butyl group to come up against the methyl group.

27. Al Kane was investigating the reduction of aldehydes and ketones with a chiral reducing agent. In a test run, he reduced 2-butanone to 2-butanol. The optical rotation of the product he obtained was -11.37 degrees. What was the enantiomeric excess of this reaction? The specific rotation of (R)-2-butanol is -13.52 degrees. Enter your answer as a 3-digit number. Do not include any units. 84.0

28. How many chiral ethers are there with the molecular formula C4H8O? 3

 

29. Draw the structure of compound D.

CC1=C(C)CCC1 Compound E undergoes an intramolecular aldol condensation.

30*.

COC(=O)[C@H]1CC=C(C)C[C@@H]1C(=O)OC or COC(=O)[C@@H]1CC=C(C)C[C@H]1C(=O)OC