Chem 118A Exam 1 - First Examination Chemistry...

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Unformatted text preview: First Examination Chemistry 118A(B) October 28, 2009 (Closed book, no models) Name (Please print) . Last First Middle initial Last 4 digits of ID Number: TA 1) This exam consists of 5 pages (including this page) and 9 questions. 2) Do not turn the pages until 4:10 pm. 3) Turn in your paper to one of the teaching staff by 5:00 pm. 4) Put the last 4 digits of your ID in the upper right corner of each of the next 4 pages. Be sure you have pages 2-5. 5) Please answer clearly in the spaces provided. The back of the pages are only for scratch work. 6) Any request for regrading should be done according to the TA’s instructions. Fall 2009 118A Exam 1 Page 2 of 5 4 digits of ID _ 1. Write the name or draw the structure where appropriate for each of the following: a. (6 Pts) €sz \ JV b. (6 Pts) C1 c. (5 Pts) W B W r d. (4 Pts) Complete the following structure for the least stable conformer of trans-1 -t-butyl-4-(2-methylpropyl)cyclohexane. e. (4 Pts) Complete the following Newman projection for the most stable conformer of neopentycyclohexane looking down the C2-C1 bond. Fall 2009 118A Exam 1 Page 3 of 5 4 digits of ID _ 2. (12 Pts) Draw ALL possible resonance forms for CH3NCO that contain only closed shell (octet stabilized) atoms?. Circle the major resonance contributor(s) to the hybrid structure. Clearly write all lone pairs (if any) and all nonzero formal charges (if any). 3. (10 Pts) Rank the labeled hydrogens in order of INCREASING acidity. (l = weakest acid). 0 Br::I>H H A H CH: C H N \ \o C/ H<————v D E ::> H3C'H2C‘O/ \\\\O E] i] [3] DD E] 4. (9 Pts) Determine whether the following pairs of structures as structural isomers, resonance forms of the same compounds, stereoisomers, conformers, identical structures, or none of the above. / ’6 ’t a. Br and “"""‘ Br b. CH2=CH-OCH3 and HOHZC—CHZCHZ CH3 H H H C2H5 C’ and CH3 B H Br C H r H3 C 2 5 CH3 Fall 2009 118A Exam 1 Page 4 of 5 4 digits of ID __ 5. (4 Pts) Draw the bond line structure for HOCOCH2CHCHNHCOCH(CH3)2 6. (6 Pts) Bromination of 1-bromopropane gives the following results: B ____2__.._._> CH3CH2CH2Br r CH3CH2CHBr2 + CH3CHBrCHzBr + CHZBrCHZCHZBr A 90% 8.5% 15% Calculate the relative reactivities of the hydrogens on each of the three carbons in the above reaction. 7. (12 Pts) Write the major organic product(s) for the monohalogenation of the following reactions. If there IS no reaction write NR. relative reactivities of the hydrogens toward chlorine: 3° : 2° : 1O 5: 4: 1 C12 a) (CH3)2CHCH2C(CH3)3 A b) (CH3)2CHCH2C(CH3)3 F2 c) (CH3)2CHCH2C(CH3)3 I2 A, hi) 8. (4 Pts) Excluding the product, what other organic compound could possibly form in the termination step of the following reaction? Br A C2H6 Fall 2009 118A Exam 1 Page 5 of 5 4 digits of ID _ 9. (18 Pts) Multiple choice. Please circle one. 0 Molecule A HO 4? OH a) The molecular formula of A is: c—bond C8H15NOS C8H17NO6 C8H17NO6 C9H15NO6 None of the above b) The hybridization of nitrogen in molecule A is: SP2 SP3 SP P None of the above c) The hybridization of a—C in molecule A is: SP2 SP3 sp p None of the above (1) The sigma bond betwenn C4-C5 bond is formed form ovelapping of orbitals. P ans p s and 5 sp and sp sp2 and sp2 sp2 and SP3 e) As of today no one has ever been able to make cyclobutyne as a stable compound because of: Cyclobutyne hyperconjugation ring strain angle strain torsional strain steric hindrance 0 Which of the following is the strongest Bronsted base? 0 O _ e e 9 e ...
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