final spring 2010c - city university of new yorkacademic.brooklyn.cuny.edu/chem/howell/chem 52/old...

Chemistry 3520, Brooklyn College, CUNY, Fall 2010

Chemistry 3520 Exam 1, Fall 2010

=============================================== This is a closed book exam. The exam lasts 50 minutes. All answers must appear on the answer sheet. Only the answer sheet will be collected. Put your name on the answer sheet now. When the exam is over you must hand your answer sheet in promptly or a penalty may be assessed. You may not leave the room during the exam. =============================================================== What are the products of the following reactions? Indicate stereochemistry where possible. Write NR if there is no reaction. Put one set of product(s) in the answer box: the final product(s) for complete credit or an intermediate product(s) for partial credit. 1.

CO2H

CHO

NaBH4

2.

3.


4.

Ph HBr

50 deg

5.

6.

========================================================== 7. Butanoic acid and pentanal have almost the same molecular weight. Butanoic acid has a higher boiling point than pentanal (163 vs 103) and the solubility of butanoic acid in water is much greater than that of pentanal. Offer a brief but complete explanation of both phenomena. 8. In the Monsanto process for the production of acetic acid from methanol and carbon monoxide [Rh(CO)2I2]

- is used as catalyst. Show the transformations for the catalyst and label each step to indicate the kind of reaction involved.


9. The following reaction occurs for the cis isomer but the trans isomer is unreactive. What is X? What is the mechanism? Use curved arrow notation.

=============================================================== 10. Shade the templates to show the LUMO and HOMO pi molecular orbitals of ethylene and buta-1,3-diene. Show the electron flow that occurs in the Diels Alder reaction to yield cyclohexene.

=============================================== Show how to accomplish the following transformations. You may use any other reagents that are needed. More than one step may be needed. 11.

12.


============================================================= 13. Grignard reagents add to carbonate esters as they do to other esters. Predict the product of the following reaction.

=============================================================== 14 A chemist wishes to perform a Claisen condensation on ethyl acetate. 88 grams of ethyl acetate and 0.1g of NaOH are mixed together and heated. The yield was found to be unexpectedly low. Give a careful analysis of what went wrong. What should be done to correct the problem? 15. Azulene, shown below, is unusual for several reasons. It possesses a dipole moment of about 1 D. Offer an explanation.


Answer Sheet

Exam 1, Chemistry 3520, Fall 2010 Your Name __________________________ Indicate your recitation instructor ( 1 pt): Appayee___; Brenner____; Howell____; McGarraugh_____; Mollica_____

1 (6)

2. (6) 3. (6)

4. (6)

5. (6) 6. (6)

7(7)

8 (7)

9. (7)


10 (7)

11 (7) 12 (7) 13. (7) 14 (7)

15 (7)


Chemistry 3520 Exam 2, Fall 2010

=============================================== This is a closed book exam. The exam lasts 50 minutes. All answers must appear on the answer sheet. Only the answer sheet will be collected. Put your name on the answer sheet now. When the exam is over you must hand your answer sheet in promptly or a penalty may be assessed. You may not leave the room during the exam. =============================================================== What are the products of the following reactions? Indicate stereochemistry where possible. Write NR if there is no reaction. Put one set of product(s) in the answer box: the final product(s) for complete credit or an intermediate product(s) for partial credit. 1.

2.

give normal drawing of product and name it. 3.


4.

5.

6.

nitric acid

sulfuric acid

reduction NaNO2

HCl, cold

aniline

7.

==========================================================


8. An amine is reacted with NaNO2 and HCl at 5 deg. Small bubbles are observed. What does this tell you about the structure of the amine? 9. The pure form of a particular aldohexose was found to have a specific rotation of 100 deg while the pure form has a specific rotation of 60 degrees. When the forms are allowed to equilibrate the specific rotation becomes 70 degrees. What is the fraction of the anomer in the equilibrium mixture? 10. The two isomers shown below yield the same product. What is it? Offer an explanation for why the same product when starting with the two different reactants.

11. Pyrole undergoes substitution rapidly to yield substitution at the 2 position as shown below. Explain both the high reactivity and the regioselectivity.

=============================================== 12. Show how to accomplish the following synthesis. More than one step will be needed.

=============================================================


13. Offer an explanation as to why acetamide is a weaker base than methanamine. H2N

O

acetamide

H2N CH3

methanamine

14 An unknown aldohexose was found to yield the same osazone as D-Galactose. What is the structure of the unknown aldohexose? Use the template provided.

complete template 15 An unknown hexose derivative was reacted with periodic acid as shown below. Provide a structure for the unknown. Omit stereochemistry.


Answer Sheet

Exam 2, Chemistry 3520, Fall 2010 Your Name __________________________ Indicate your recitation instructor: Appayee___; Brenner____; Howell____; McGarraugh_____; Mollica_____

1 (6)

2. (6) 3. (6)

4. (6)

5. (6) 6. (6)

7(6)

8 (7)

9 (7 )


10 (7)

11 (7) 12 (10) 13. (7)

14 (7)

15 (7)

Brooklyn College, CUNY Chem. 52 NAME______________________ Recitation Instructor____________________

Chemistry 52 Spring 2010 Final Exam

1. This is a two hour, closed book exam. All answers are to be put on the question sheets. 2. Use the backsides of these pages for scratch paper. None other permitted. 3. At the end of the exam pass in all exam material. 4. There are 17 questions. Make sure you have all of them. All questions are worth 6 points. 5. Write your name on all pages of this exam. Do it now!

1. 4-hydroxybenzoic acid melts significantly higher than 2-hydroxybenzoic acid as shown below. Offer an explanation.

What are the products or missing reactants of the following reactions? Indicate stereochemistry and, where provided, make use of as many templates as needed. 2

3.


4.

5.

nucleophilic carbenecatalyst

6.


7.

8. Methyl acetate undergoes acid catalyzed hydrolysis. The reaction is done using H2

18O and is stopped before complete hydrolysis takes place. The methyl acetate is recovered and it is found that some of the methyl acetate has been transformed into the labeled compound shown below. Provide a mechanism by which this can happen.

9. While attempting to identify an unknown water insoluble liquid compound (mp < 0 deg and bp approx. 190 deg) containing nitrogen a student attempts an acid catalyzed hydrolysis. A product of the hydrolysis (mp approx 130 deg) was isolated and found to be insoluble in both dilute cold aqueous acid or base. It was found to contain nitrogen. Suggest an explanation including a mechanism for the transformation.


10 Offer a discussion of the following reaction. What are the interesting aspects of the product and how did they happen?

11 The following is the structure of cholesterol without any stereochemistry. Indicate on the diagram all stereoscopic aspects of the molecule by using wedges and dashed lines.


=============================================================== Provide a synthesis of the following compounds. Use only ethanol, benzene and inorganics as the source of all carbon atoms in the target molecules. In later problems you may also use as starting material target molecules of earlier problems even if you were not able to solve the earlier problem. Do not repeat synthetic work. You may reference a compound prepared in an earlier problem by a symbol such as 11A referring to compound A in Problem 11.

12

13.

14 When RNA is hydrolyzed there is no relationship among the quantities of the four bases obtained in contrast to the results observed for the hydrolysis of DNA. What does this suggest about the structure of RNA?


15. The A chain of beef insulin contains 21 amino acids and has the empirical formula

GlyAlaVal2Leu2IleCys4Asp2Glu4Ser2Tyr2

Edman degradation yields Gly. The C-terminal group is known to be Asp Acidic hydrolysis yielded Cys-Cys-Ala Glu-Leu-Glu Cys-Asp Glu-Asp-Tyr Leu-Tyr-Glu Tyr-Cys Glu-Cys-Cys Ser-Leu-Tyr Gly-Ile-Val-Glu-Glu Glu-Glu-Cys Ser-Val-Cys

A) The above data does not permit the complete determination of the structure. Construct as much of the N terminal end of A Chain as the data will reliably allow.

Pepsin hydrolysis of the A chain yielded a peptide that contained neither Asp nor Tyr. Hydrolysis of the peptide yielded products including Ser-Val-Cys and Ser-Leu

B) Propose a complete structure for the A chain.


16. a) Consider the free radical polymerization of ethylene and show what is meant by chain transfer reactions. b) Chain transfer is much more common in the free radical polymerization of ethylene than in the free radical polymerization of styrene. Offer a detailed, complete explanation. 17 Answer by letter. A. What sequence is fully complementary to the following sequence? 5’-ATCTAGTCA-3’

a. 5’-TAGATCAGT 3’ b. 5’-TGACTAGAT-3’ c. 5’-ATCTAGTCA 3 d. 5’-ACTGATCTA-3’

B. How many bases are present in each strand of a complete turn of B-DNA? a. 3 b. 7 c. 10 d. 15

C Which of the following is a definition of messenger RNA (mRNA)? a. RNA found in the ribosome, the site in cells where synthesis of proteins takes place b. RNA which carries a specific amino acid to the site of protein synthesis c. RNA which has coded genetic information d. RNA which signals cell death

Quiz 6, Spring 2010 Chemistry 52 Name_______________________________

Answer by letter at the bottom of this sheet 1. What is the structure of stearic acid? a. CH3(CH2)16COOH b. CH3(CH2)7CH=CH(CH2)7COOH c. CH3(CH2)18COOH d. CH3CH2(CH=CHCH2)3(CH2)6COOH

2. How many triglycerides (including stereoisomers) are there which contain two molecules of stearic acid (18:0) and one of arachidic acid (20:0)? a. 3 b. 6 c. 9 d. 12 3. Which of the following fatty acids has the highest melting point? a. stearic acid (18:0) b. oleic acid (18:1) c. linoleic acid (18:2) d. linolenic acid (18:3) 4. Which of the following is not true? a. sodium soaps are prepared by saponification of triglycerides b. a by-product of the saponification of triglycerides is glycerol c. soap molecules assemble into micelles d. grease molecules absorb on to the surface of micelles 5. Which of the following processes is used to harden an oil to give a fat? a. oxidation b. hydrogenation c. hydrolysis d. hydration Answer by letter

1 2 3 4 5

Quiz 6

What are the products of the following reactions. Show stereochemistry

1

NHexcess CH3I Ag2O heat

2.

NH

NaNO2, HCl

Which of these is the strongest base? Which is weakest?

N

HN

Ph

H3C H

N(CH3)2

H CH3

H2O2 heat

3

4

5. Starting with benzene propose a synthesis of 1,2-dichlorobenzene.

NH2NH2

NO2

N(CH3)3

H2N NH2

NH

Quiz 7 Chemistry 3520, Fall 2010

1. How many triglycerides (including stereoisomers) are there which contain two molecules of stearic acid, and one of myristic acid?

2. What is the R/S configuration of C-8 and C-12 of prostaglandin F2α?

3.

HO

HO

COOH

OH

8

12

3, Shown below are two aldopentoses. Give a simple chemical procedure to distinguish between them.

CHO

HO H

H OH

CH2OH

H OH

CHO

H OH

HO H

CH2OH

H OH

4. Shown below is the structure of maltose

a) Is this a reducing sugar? Explain

b) What are the characteristics of the bond linking the two glucose units?

c) Does maltose undergo mutarotation? Explain

O

H

HO

H

HO

H

OHHH

OH

O

O

H

H

HO

H

HO

OHHH

OH

Chemistry 3520Fall 2010, Quiz 8

1. What is the isoelectric point of arginine?The acidity constants of the acidic forms ofthe acid/base centers are shown. NH2

CO2HNH

H2N

pKa = 12.5

pKa = 2.0

pKa = 9.0

2. Draw a titration curve for one mole of arginine dication with sodium hydroxide. Show thedominant species present at each pH range

moles NaOH added.

2

4

6

8

10

12

1 2 3 4

pH

3. Give a careful comparison of the helix and the pleated sheet forms of polypeptides.

final spring 2010c - city university of new yorkacademic.brooklyn.cuny.edu/chem/howell/chem 52/old...

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