CHEM 237 exam_answers_Final Exam_key

CHEM 237 exam_answers_Final Exam_key - [24/ Chemistry 239...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 10
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: [24/ Chemistry 239 Autumn, 2007 Final Exam Answer Key Your name: Student #: Sign here to indicate your approval of public return of your paper: 1 (21 pts.) Give IUPAC names or structures for the compounds below. C6H5C02', K+ CH3CH2C02COCH2CH3 CH3(CH2)2CN potassium benzoate propanoic anhydride butanenitrile PhCH.2N(CH3)3+, Br' CH3 benzyltrimethylammonium bromide 1-methylbenzyne 02H HZOCOR R'co2 H CHZOCOR" a triacylglyceroi D-mannaric acid Fischer projection 2 (5 pts.) Write a balanced equation for a proton transfer between the reactants below and indicate whether the equilibrium will be favorable (to the right) or unfavorable (to the left) for the process. Note: the pKa of NH4+ is 9.3. unfavorable Chem 239 Autumn, 2007 Final Exam Answer Key p. 2 3 (5 pts.) Draw the chair structure for methyl 0L -D-allopyranoside. methyl a-D-allopyranoside 4 (27 pts.) In the reactions below fill in the missing items (starting material[s], reagents and conditions over the arrow, or main organic product[s]). A9(NH3)2+. 0”- CH3OH C6H5COC| —-——> CsHSCOZCH3 1.Eto' 2. H30+ CH3CH(CH2CH2C02CH2CH3)2 m» Fe, HCI or Hz/cat OZN‘"©—Et ~——-———————> HZN Et (l2H3 heat Ph-O-CHz-C=CH2 -——> m COZCHZCH3 HCN CN ' D' ‘ orfl5 Ag+INH3 H'CO'(CH2)4-CH20H m“> O-—CO'(CH2)4'CH20H Chem 239 Autumn, 2007 Final Exam Answer Key p. 3 5 (12 pts.) Write a balanced equation for the reaction you would expect between the reactants below. Beneath the equation draw a curved arrow mechanism for the reaction. (Show all bond formation and bond rupture steps, unshared electron pairs and formal charges.) CI-COzEt + EtOH —» EtOCOZEt + HCI 6 (12 pts.) Give your interpretation each item of evidence below and propose a structure for a compound I. A) Mol. wt. of I = 129). B) The IR spectrum of I had a single peak between 3300—3500 cm'l' and no absorption around 1700 cm'. I gave the nmr spectrum below — show your peak assignments and label the multiplicity of all peaks. (Show your reasoning for partial credit.) (CH3)3CNHCH2CH(CH3)2 a) odd mass,single N, b) 2° amine, no C=O mol. wt. C8H19N' = (8x12) + 19 + 14 = 129 Chem 239 Autumn, 2007 Final Exam Answer Key p. 4 7 (10 pts.) Show how you would carry out the syntheses below. (Show the main product after each step, with reagents and any special conditions over each reaction arrow.) Ph Ph UCOCI from \[:>‘Br 8 (8 pts.) Draw a curved arrow mechanism for all steps in the reaction of the ether below with HI. Show all unshared electron pairs, and formal charges. CSHS'OrCHzCGHs + H—I 0F Cox/la! 0(0 5N1 —> C5H5'6H + -'- l-CH2C5H5 Chem 239 Autumn, 2007 Final Exam Answer Key p. 5 9 (10 pts.) Show your conclusions for each observation and draw a structure for a disaccharide that gives the results below. (Show cyclic chair conformations for all structures.) a) Gives a positive Tollens test and shows mutarotation. free hemiacetal, so only one carbonyl combined in glycoside linkage b) Hydrolyzed by oc—glycosidase, but not B—glycosidase, enzymes, giving D—galactose and D—mannose. one galactose and one mannose, a—link to the glycoside carbonyl c) Methylation followed by hydrolysis gives 2,3,4,6—tetra—O-methyl-D-galactose and 2,3,4—tri—O—methyl—D—glucose. (Here need only show disaccharide structure.) Chem 239 Autumn, 2007 Final Exam Answer Key p. 6 11 (18 pts.) Give the structures for. cysteine dicyclohexylcarbodiimide ONzczN—O (show ionic form at pH 7 and both, 3-letter and 1-letter abbreviations) proserphe H - HCO-NHCHCO-NHCHCOZH 2'-deoxy-1- B-D-ribofuranosyithymine 6-aminopurine cytosine 12 (8 pts.) For the amino acid aspartic acid (below) the pKa values are 1.9 (OL— COZH) , 9.6 (oc-NHf) and 3.7 (side chain function). cHzcozH HZNCHCOZH Draw the predominant form of aspartic acid at its isoelectric point and briefly explain whether the isoelectric point would be more acidic or more basic than glycine (which has p1 = 6.0). CHZCOZH more acidic, greater amount H CO _ l of this anion to protonate (A ‘1: 2 i-BNCHCOZ + H3NCHCO{ as well as some dianion wswmzmmmmwmmmmsm— W, n . .. . . Chem 239 Autumn, 2007 Final Exam Answer Key p. 7 13 (24 pts.) In the reactions below fill in the missing items (starting material[s], reagents and conditions over the arrow, or main organic product). CN',NH3 THZ THE QCHZCHo—w» CHZCHCN ————>E>—CHZCHCOZH $02“ 1. EtO' $02“ “30+ CH3 CHNHCOCH3 ——-———> CH3CNHCOCH3 —> HZNCHCOZH | 2. CH3Br I COZEt COzEt heat CH CO Et l 2 2 ‘ H2, cat. PhCHZOCONHCHCOZCHzPh ————-——> HZNCHCOZH CHzcozEt CH CH Ph PhN=C=S, H+ Ph CH Ph 1 3 I 2 SYN l 2 HzNCHCONHCHCOZCH3 :0 + HZNCHCOZCHg HN HZNCHCOZMe + PhCHZOCONHCHCOZH ——> PhCHZOCONHCHCCNHCHCOZMe Chem 239 14 (8 pts.) 15 (8 pts.) Autumn, 2007 Final Exam Answer Key p. 8 Amino acid analysis of a nonapeptide I gave the composition: 2Ala, Cys, 3Gly, Phe, Pro, Ser. Reaction of the I with Sanger’s reagent gave DNP~Gly. Partial hydrolysis of I gave the following fragments: AlaGlyCys, AlaProPhe, CysAla, GlySer, PheGly, and SerAla Propose a structure for I and show your reasoning. AlaGlyCys CysAIa AlaProPhe PheGly SerAla GlySer GIySerAIaGlyCysAlaProPheGly Show the reactions (with reagents) you would use for the synthesis below. (Show intermediate products after each step.) FMOC-AIa-AIa-Ala-OCHZPh from FMOC-Ala-OCHzPh H2, cat. NH3 FMOC-Ala-OH DCCI FMOC-AIa-OH + H-Ala-OCHzPh DCCI NH3 <——-—- H-Ala-Ala-OCHZPh FMOC-AIa-AIa-OCHzPh Chem 239 Autumn, 2007 Final Exam Answer Key p. 9 16 (8 pts.) Show the hydrogen bonding for the specific base pairing between adenine and thymine. Next draw how a tautomer of guanine might replace adenine and hydrogen bond to thymine. G tautomer 0—HWO / \ N11” H““N H N’HWO / H 17 (7 pts.) Draw a segment of the DNA structure, showing at least two sugar units (use single letter abbreviations to represent the heterocyclic bases cytosine and thymine) . ‘zmwmmmm‘xM—mk e TABLE 13.17 Compound class or type.of proton I V - , ‘ Chemical shift (8), ppmt.‘ i Protons bonded to carbon ' Alkane . ' v RCH3, RZCH27R3CH . 0.9—1.8“- ' / . ' * H—C/ Allylic - ‘\ _C/ .1.5—_2.6 . . . /‘ \ _ - / - H—C/ C——H adjacent to C=O \ . _ 2.0—2.5 . C==0 _ ~ / . ' ' I i C—-H adjacent toC‘=—.N . H—Cl—CEN _ r . 2.1—2.3 Alkyne ' H—CEC—R . 2.5 3 .I I ’ I > Benzyllc ’ V H—.Cl——Ar ‘ . ~ 2.3-2.8 - i . Amine ~ _ H—_—(lZ—'_-NR‘2 2.2—2.9 _ - Alkylchlonde H—Ci—Cl . 3.1—4.1 Alkylbromlde ‘. . I H—Cl—Br _ 2,7—4.1 V V . I -_ ’ Alcohol or ether , H—Cl—O 3.3—3.7 : H\ / v Vinylic' . c=c 4.5—6.5 - / \ > _ ' Aryl , H—Ar - . 6.5—8.5 R\ Aldehyde /C=O ‘ 9—10 - H Protons bonded to nitrogen or oxygen 1 Amine H——-NR2 ~ 1—-3'r Alcohol H—OR 0.5—5f Phenol H—‘OAr ' 6—8‘ ' ‘ ‘u’ Carboxylic acid ' , H--0CR 1043* > *Approximate values relative to tetramethylsllane; other groups Within the molecule can cause a proton signal to appear outside of the range cited. ‘ 'Th'e chemical shifts of 0—H and N—H protons are temperature- and concentration—dependent. . ...
View Full Document

Page1 / 10

CHEM 237 exam_answers_Final Exam_key - [24/ Chemistry 239...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online