Unformatted text preview: Exam 1 Wednesday, September 21, 2009 Chem 2111 Instructions: Detach the back answer sheet and fill in your name and your TA's name. Fill in all answers on the answer sheet. Turn in the answer sheet only for grading. Do not turn in this exam quest ion booklet it will not be graded. Note: There are 11 pages including this cover page and attachments. Each page is numbered. You are responsible for having all 11 pages. If a page is missing, please obtain a new exam. Problems 120, 20 mult iple cho ice problems, 4 pts each (total 80 pts). Problems 21 and 22, 2 boxes, 10 pts each (total 20 pts). Total exam (100 pts) Attachments: Answer Sheet 1 1. Which pairs o f structures are constitutional isomers? CH 3 H C 3 CH 3 a CH2 3 CH CH CH 2 3CH 2CH CH3 CH3 CH CH CH 3 2CH2 CH2 CH3 c b H 3C CH CH CH 3CH2CH2 2 d 2. Which structure represents a ketone? O CH CH C OCH 3 2 3 a O CH CH CH 3 2 b O CH CCH 3 3 c O CH COH 3 d 3. Which bond has the largest bond dipole mo ment? O H a C N b C O c C S d 4. Which chair structure corresponds to the planar hexagon ring shown? C H 3 CH 3 CH 3 CH 3 a CH 3 CH 3 C H 3 b CH 3 CH CH 3 3 c CH 3 CH 3 d CH 3 CH 3 C H 3 5. In HC≡CH, which AOs are contributed by each carbon to form the triple bond? A B C D one A one B a one C two B b one D one C c one D one A d 2 6. Which is the IUPAC name for the structure shown? a 1(1,1dimethylethyl)4ethylcyclohexane b 1ethyl4 (2,2dimethylethyl)cyclohexane c 1ethyl4tertbutylcyclohexane d 1ethyl4(1,1dimethylethyl)cyclohexane 7. Which structure is a tertiary amine? CH CH N (CH ) 3 2 3 2 a CH CH N HCH( CH ) 3 2 3 2 b (CH3 3 H ) CN 2 c O CH C N(CH ) 3 3 2 d 8. Which Newman project ion does not represent 2methylhexane? H H CH 3 H CH 3 CH CH CH 2 2 3 a H H CH(CH 3)2 H H CH CH 2 3 b CH 3 H CH H 2CH2C 3 H H H CH 3 c H H CH H H 2C 2C 3 CH 3 CH 3 d 9. Which pair of structures are conformers? CH 3 CH 3 A A and B a B CH3 CH 3 CH 3 CH 3 C D B and D d H C 3 CH 3 A and C b B and C c 10. Which pair of structures are not valid resonance contributors?
HC NH a O H C C CH 2 3 d HC NH CH N C O 3 b CH N C O 3 CH CH CHC H 3 3 c C H CH CH CH 3 2 2 O H C C CH 2 3 3 11. Which of the structures below is the most stable const itutional iso mer? Heats of combust ion (kcal mo l 1 in parentheses) are as fo llows: octane (1307.5), 2methylheptane (1306.3), 2,2 dimethylhexane (1304.6), and 2,2,3,3tetamethylbutane (1303.0). a b c d 12. Which is the IUPAC name o f the alkane shown? a b c d 3propylpentane 1,1diethylbutane 3ethylhexane isooctane 13. Which compound has a net dipo le mo ment? NH 3 a CO 2 b B F 3 c CCl 4 d 14. Which structure should have a net charge? BH 3 a CCl 4 b H S 2 c BH 4 d 15. Which is the most stable conformer of cis1isopropyl3methylcyclo hexane? CH 3 CH (CH ) 3 2 CH (CH ) 3 2 CH(CH ) 3 2 CH 3 a b CH 3 c d CH 3 CH(C H ) 3 2 16. Which compound has a carbon that is d+?
CH 4 a CH OH 3 b CH Li 3 c (CH ) Si 3 4 d 4 17. Which structure represents the most stable conformat ion of 2,3dimethylbutane? CH 3 H CH 3 H CH3 CH 3 a H H CH 3 CH 3 CH 3 CH 3 b H H CH 3 H CH 3 CH 3 c H CH 3 CH 3 H CH 3 CH 3 d 18. Which structure should have a posit ive formal charge on nitrogen (no formal charges are shown in any structure)? NH CH N C: 3 a CH C N: 3 b CH NH 3 2 c H N 2 C d NH 2 19. Which would be the difference in heats of combust ion for the structures shown (in kcal 1 mo l )? CH 3 CH 3 CH3 CH 3 0 a 0.9 b 1.8 c 2.7 d 20. What are the approximate HCH bond angles in [CH3] ? 90° a 109° b 120° c 180° d 5 2123. Draw in the appropriate boxes proper projections o f the staggered and the eclipsed structures of (CH3)2CHCH3. What is the energy difference ( in kcal mo l 1 ) between the eclipsed and staggered structures of (CH3)2CHCH3 (Note: the eclipsing strain for a pair of CH bonds is 1.0 kcal mo l 1and for CH and CC bonds is 1.4 kcal mo l 1 )? 12 pts (4 pts each box) answer sheet answer sheet answer sheet 21. staggered structure 22. eclipsed structure 23. energy difference 24. Write inside the box the most stable chair conformer of cis1,3dimethylcyclo hexane. (4pts) structure an swer sheet 25. Draw inside the box a structure of H2C=CH2 which shows all appropriate orbitals at each atom and the overlaps of these orbitals with each other. Label each orbital as to its type (s, p, sp, 2 3 sp , sp ). (4 pts). structure an swer sheet 6 Chem 2111 Exam 1 Answer Sheet Name:_____________________________ TA: _______________________________ 1 A 2 A 3 A 4 A B B B B C C C C D D D D 5 A 6 A 7 A 8 A B B B B C C C C D D D D 9 A 10 A 11 A 12 A B B B B C C C C D D D D 13 A 14 A 15 A 16 A B B B B C C C C D D D D 17 A 18 A 19 A 20 A B B B B C C C C D D D D problem 21 staggered problem 22 eclipsed prob lem 23 energy difference problem 24 chair problem 25 orbital diagram 7 ...
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