CH310M-Exam1_KEY[1] - CH 310/318M EXAM 1 Williams— Fall...

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Unformatted text preview: CH 310/318M - EXAM 1 Williams— Fall 2010 EID: Name (print): Signature: Do Section I (Scantron) in #2 Pencil! Do Section II in blue or black PEN! Please write the first three letters of your last name in the boxes CH 310/318M - EXAM 1 Williams — Fall 2010 EID: .- 6 12 7 12 Section II 125 m- -— CH 310/318M - EXAM 1 Williams - Fall 2010 EID: PART 1 MULTIPLE CHOICE (5 PTS EA: 125 PTS in this section) 1) Which of the following is true? a. Molecules with stereocenters are always chiral. b. A chiral center is not a requirement for chirality. CORRECT c. A meso compound is not chiral because is lacks the presence of a chiral center. d. A chiral center is a carbon center with three or more different groups attached to it. 2) Which of the following resonance structures makes the largest contribution to the structure of [HZCCHO]? .6 “e G) :fi: :T: :T: :T: e C c e 0‘9 o (3 --/ \ / \ .. .. HZC H HZC/ H ch/ \H HZC/9\H 1 <9 3 4 a.4 b.3 C. 2 CORRECT d.1 3) Which atomic orbitals overlap to form the C-0 bond of diethyl ether, (CHSCHZhO? a.Csp3vi—Osp2 W v b.Csp2+Op \/ c. Csp2 + 0 5p2 CH 310/318iVl - EXAM 1 Williams — Fall 2010 EID: d. c 5p3 + 0 5p3 CORRECT 4) What is the approximate C-C-C bond angle in propene, CH3CH=CH2? 3. ° H H L; v< c/ n c. 120° CORRECT 3 d. 180° 5) Which of the following structures is different from the other three? CHacHZWTcns J: 23% j; BF H CiiZBCHg HBCH Br CHagHz CH3 1 2 3 4 a. 1 b. 2 C. 3 CORRECT d. 4 6) Which of the following best represents the shape of a 2p atomic orbital of carbon? 0 8 l? 88 a. 1 b. 2 CORRECT c. 3 d.4 CH 310/318M - EXAM 1 Williams — Fall 2010 EID: 7) What functional groups are found in the high blood pressure treatment, Captopril? SH 0 COOH O|||llln I DJ 3. thiol, ketone, carboxylic acid, amine b. alcohol, amide, carboxylic acid c. thiol, amide, carboxylic acid CORRECT d. amide, ketone, carboxylic acid 8) Which of the following statements is not true regarding resonance structures? a. All resonance structures must have the same number of electrons b. Each atom in all ofthe resonance structures must have a complete shell of valence electrons CORRECT c. All resonance structures must have the same arrangement of atoms d. All resonance structures must be valid Lewis structures 9) Which of the following statements is not true about the carbonate anion, C03}? a. All ofthe oxygen atoms bear the same amount of charge b. All of the carbon—oxygen bonds are the same length c. The carbon atom bears the negative charge CORRECT CH 310/318M — EXAM 1 Williams— Fall 2010 EID: d. It is basic 10) Which of the following resonance structures is the least important contributor to the resonance hybrid of the acetate anion, CH3COO'? “0.. "(5&9 “o: "of-6 // / / / ch—C chwc\\ H3c—C\:E) H3C—C69 0 e -.o" «939 o e 1 2 3 4 a. 1 b. 2 C. 3 CORRECT d. 4 11) Which of the following Newman projections represents the most stable conformation of 2—methylbutane? CH3 CH3 CH CH H 3 H CH3 H CH3 H 3 CH3 H H H H CH3 H CH3 H30 CH3 CH3 H H H 1 2 3 4 a. 1 CORRECT b. 2 c. 3 d. 4 CH 310/318M - EXAM 1 Williams — Fall 2010 ElD: 12) Which of the following is the most stable conformation of cis—l-isopropyI—3-methylcyclohexane? CH(CH3)2 CH(CH3)2 q CH3 l CH3 CH(CH3)2 New“,ng H30 H30 .1 2 3 4 ct‘: «\wm 9 of 9 JMmS a. 1 ‘O‘Q 0km 10.2 “‘“o c. 3 CORRECT d. 4 13} Which of the following compounds has 1“, 2°, 3° and 4“ carbon atoms? a. hexane b. 2—methylhexane c. 2,2-dimethylhexane d. 2,2,3-trlmethylhexa ne CORRECT 14) Which of the following substituted cyclohexanes has the most negative value of 136° for ring flipping from the conformation in which the substituent is axial to the one where it is equatorial? a. fluorocyclohexane b. tert-butylcyclohexane CORRECT c. ethylcyclohexa ne d. methylcyclohexane CH 310/318M — EXAM 1 Williams — Fall 2010 EID: 15) Which of the following statements is not true? a. Combustion of an alkane is an exothermic reaction. b. The constitutional isomers of C7H15 have different heats of combustion from one another c. The heat of combustion of propane is three times that of methane. CORRECT d. The products of combustion of an alkane are H20 and C02. 16) Which of the following alkanes has the highest boiling point? a. 2,3-dimethylbutane b. 2-methylpentane c. 3-methylpentane d. hexane CORRECT 17} What is the IUPAC name ofthe following compound? a. 2.." s a. trans-l-isopropyl—4—methylcyclopentane b. cis-1—tert—butyl—Z-methylcyclopentane c. trans-1~tert-butyI—Z-methylcyclopenta ne CORRECT cl. cis-1-isopropyI-Z-methylcyclopentane CH 310/318M - EXAM 1 Williams — Fall 2010 EID: 18) Which one ofthe following structures represents a different compound from the other three? CH3 CH3 H H3 H3 H H mom/CH3 H30 H H H CH3 1 2 3 4 a. 1 b. 2 c. 3 CORRECT d. 4 19) Which of the following substituted cyclohexanes has the most negative value of AG" for ring flipping from the conformation in which the substituent is axial to the one where it is equatorial? a. methylcyclohexane b. chlorocyclohexane c. ethynylcyclohexane d. isopropylcyclohexane CORRECT 20) Which of the following statements is not true regarding the conformation of substituted cyclohexanes? a. ring inversion of cyclohexanes between two chair conformations takes place via a boat conformation b. substituted cyclohexanes are destabilized by 1,3—diaxial interactions c. the boat conformation of cyclohexane is more stable than the chair conformation CORRECT d. the relative amount of two conformations of substituted cyclohexanes can be determined from the difference in strain energy 21) Which of the following structures represents trans-1,3-dimethylcyclohexane? CH 310/318M - EXAM 1 Williams— Fall 2010 ED: wig Aflxfl a. 1 b. 2 CORRECT c. 3 (1.4 22)Which of the following statements is not true regarding pairs of enantiomers? a. They have identical melting points b. They have identical boiling points. 0. They rotate plane polarized light in opposite directions d. They react at identical rates with chiral reagents CORRECT 23) Which of the following compounds is/are chiral? W a. only 1 CORRECT b. only 1 and 2 c. only 2 and 3 d.1,Zand3 24) Which of the following have the R configuration? 10 CH 310/318M - EXAM 1 Williams — Fall 2010 EID: /TK C/HE Br CH2CH2CH2CH3 ""“CH CH H 0% 2 3 H c 3 H30 NH2 2 sCH H H CH(CH3)2 1 2 3 a. only 1 b. only 2 c. only 1 and 2 d. 1, 2 and 3 CORRECT 25) What is the correct order of the Cahn—Ingold—Prelog ranking of the following substituents as used in assigning R and S configurations of chiral centers? (higher ranking > lower ranking) 1. —CECH 2. —CH2NH2 3. —NHCH3 4. —CN a.3>4>1>2 b.4>3>1>2 C.3>4>2>1CORRECT d.4>3>2>1 END OF SECTION 1 11 CH 310/318M - EXAM 1 Williams — Fall 2010 EID: PART 2 - Short Answer Format {125 PTS in this section) 1) Resonance. Draw the other remaining resonance structures for benzyl cation given below. Used curved arrows to indicate the flow of electrons in the formation of each resonance structure. Be sure to include all lone pair electrons and don’t forget the charge! (14 pts — structures 6 pts, arrows 4 pts, charge and lone pairs 4pts ): CH2 ‘— J (+3 (9 CH2 CH2 4—)— ® remember benzene resonance structures: 12 CH 310/318M - EXAM 1 Williams — Fail 2010 EID: 2) Name the following according to IUPAC rules for nomenclature. Please provide the name in the numbered spaces provided. (16 pts) 2— isopropy] -5-mczh_\_-'lcyc Iohcxanol 0% Q’W (331.10 1. 1. 3—1 sopropyl- 3.4-(11mCIhyI pcnlzmaun inc 2. (2.8233)- 2-Chlor0-3—i odohulunc 3. (ZS)—5—scc-but}'l-E-hyde} -‘)_‘)—dimc[h§ Idccunui 4. NH2 OH HSC H" H\“‘ I 3 (from notes!) 13 CH 310/318M - EXAM 1 Williams - Fall 2010 EID: 3) (2 pt each) For the following TRUE and FALSE questions, CIRCLE THE LETTER OF ALL THE FALSE STATEMENTS (A, B, C, etc). This is not meant to be tricky, but please read the statements carefully so that you do not make any careless mistakes. A. Resonance contributing structures are used when more than one structure are required to describe accurately how the electrons and charges are distributed in a molecule. B. For organic chemistry, it is best to think of electron density as waves, described by wave equations. C. Resonance contributing structures do not represent equilibrating structures, rather the hybrid (blending) of them is the true molecular representation. @hen drawing resonance contributing structures you generally move atom nuclei and sigma bonds. E. All (+) enantiomers are dextrorotatory. F. All (+) and H enantiomers rotate plane-polarized light in opposite directions. @or equal resonance contributing structures: full octets are favored, more covalent bonds are favored, fewer charges are favored, and a negative charge on more electronegative atom (also positive charge on less electronegative atom) are favored. H. All (-) enantiomers rotate plane-polarized light in a counterclockwise direction. I. According to the valence bond approach, the atomic orbitals on each atom are combined (hybridized) first, and bonds are derived from overlap of hybridized orbitals. “ spg hybridized carbon atom has only two major hybridized orbitals, arranged in a bent geometry. 3* II R enantiomers are dextrorotatory. L. A sigma bond occurs when the majority of the electron density is found on the bond axis. M. Equivalent resonance contributing structures make equal contributions to the resonance hybrid. N mirror images are enantiomers. 0. II molecules that have stereocenters are chiral. P. Isomers that are not super-imposable on their mirror images are enantiomers. Q. Resonance contributing structures are used when more than one structure is required to describe accurately how the electrons and charges are distributed in a molecule r organic chemistry, it is best to think of electron density as particles, described by Newton's laws. spg hybridized carbon atom has only one major hybridized orbital. T. An spg hybridized carbon atom has four major hybridized orbitals, arranged in a tetrahedral geometry. l4 CH 310/318M - EXAM 1 Williams — Fall 2010 ElD: ® pi bond ocwrs when the majority of the electron density is found on the bond axis. orsional strain is when non-bonded atoms separated by three bonds are forced from an eclipsed to a staggered conformation. @n the conformational analysis of butane, the “anti” conformation is the staggered conformation in which h e methyl groups are the maximum distance apart and have a dihedral angle of 120°. X. The gauche conformation is when they are staggered and closer together, with a dihedral angle of 60°. Y. Angle strain is when a bond angle is compressed or expanded compared to its optimal value. @Cycloalkanes adopt different conformations to relieve certain types of strain. Typically, an increase in orsional strain in less significant than an increase in angle strain AA. Cyclohexanes undergo chair “flips”, where one chair conformer converts to the other chair conformer. The interconversion between two chairs is best summarized as the following: one must first adopt a twist boat conformation, then boat, followed by the other twist boat, which finally results in the opposite chair conformation. i he energy typically associate with the chair flip for cyclohexane is 5 kcal/mol. CC. Stereoisomers are compounds with the same molecular formula, different connectivity and different ientations of their atoms in space. 15 CH 310/318M — EXAM 1 Williams— Fall 2010 EID: {Jar/g C"? ‘L 4) Consider the structure of 2,3-dimethylbutane. (30 pts total) a. Draw all staggered Newman projections and circle the lowest energy conformation. (Bpt) vl H c ' Qua W U”? \L C”? 9 5% H lat» “1, W “x ( “‘3 -. 04,, \ / ’5 lg: '4 >1 s: u i H \kw’ n (“5 (00 ' l°°' lgo - b. Draw all eclipsed New an projection nd square the highest ene y conformatio . (DD [00 . 0445 u coo' ' \U’lb w} l’l’ Ul a llng CH3 “ l’cm' o'l‘to- O. 16 CH 310/318lVl — EXAM 1 Williams — Fall 2010 EID: 4.) Continued. .. c. Plot the energy vs. dihedral energy profile for 2,2~dimethyl butane, starting with the highest energy conformation and account for all staggered and eclipsed conformations from 0-3600. include in the diagram the Newman projection for each 600 rotation (14 pts). The approximate values for torsional strain are given: Eclipsed H—H: 1.0 kcal/mol Eclipsed H"CH3: 1.2 kcal/mol Ebgl‘ ed CHg—CHg: 4.0 kcal/mol Gauche GHQ-CH3: 0.9 kcal/mol if"? 3' flow, "3" '5 a H 1 $95 “5 (kcaI/mol) 1+ 1 [kg [QM/t I 60‘: 120” 1:320” 240° 300° 360° H, w W; 3 COO H I (M; 44/ F—v % GO ————«("0. 7 C”) H all C vQY'é: c.“ \3‘ a u!“ (.0 a A70 KEMLQIM Also \‘32: H . H30 - _a/. H 60 3 ‘00 v u CH H 3 X a at) “3 4 17 H 5”} M .b -H I?“ qxlflgka 2'40 W. 953; qumQ CH 310/318M — EXAM 1 Williams — Fall 2010 E10: 4} FOR THOSE THAT 010 NOT FIX THE TEST: _Consider the structure of 2,2-dimethylbutane. (30 pts total) a. Draw all staggered Newman projections an ‘ Ie the lowest energy conformation. (Bpt) “15°”; ., €1.05“? “ I“ 0" lam Mm WW pea-M. / b. Draw all eclipsed Newman projections and square the highest energy conformation. (8pt) 5”? ‘ WW 8W9 W W (1‘45 l” as We W] M if H ‘ 18 CH 310/318M - EXAM 1 Williams— Fall 2010 ElD: 4.) Continued. .. (2. Plot the energy vs. dihedral energy profile for 2,2—dimethyl butane, starting with W conformat‘ n and account for all staggered and eclipsed conformations from 0-3600. Include in the diagram the Newman projection for each 60° rotation (14 pts). The approximate values for torsional strain are given: Eclipsed H-H: 1.0 kcalimol Eclipsed H—CH3: 1.2 kcallmol Eclipsed CH3-CH3: 4.0 kcal/mol Gauche CH3’CH3: 0.9 kcallmol «H lo-"l E (kcal/mol) W wt.) 14 3 0'73 50° 120° 130° 240° 300° 360° \lw" X "shah _ l .0 “BC. Uq #1 r ‘9 its). 1-2.. l8 Kalli/M “a, \w.) fikmD/wQ ll H ° “ 0H q % O'xllO'QLl' w (00', 1%0‘, 905- l Ola 5) Stereochemistry. Fluticasone is a glucocorticoid drug that has been used to treat asthma. Answer the following questions based on the given structure. (13 pts) 19 Williams— Fall 2010 EID: CH 310/318M - EXAM 1 none E How many chiral centers does Fluticasone have total? (1pt) 3) 9 b) How many possible stereoisomers exist for Fluticasone? (2pt) 5 12 or 2 For the indicated carbon centers, assign stereochemistry as R, S or none. Write your answer on the flat c) part of each arrow pointing at the carbon in question. (10 points) 20 CH 310/318M - EXAM 1 Williams — Fall 2010 EID: 5) Mesa Compounds. (#331 in the book!) Circle the mesa compounds from the following list: Br Br “I H” H\“‘ "UCH3 H30 H OH CH3 OH CHO CHEOH H \ OH H \ OH H OH H OH CHZOH CHgoH CH 310/318M - EXAM 1 Williams— Fall 2010 EID: 7.) Below is the structure for diazomethane, CH2N2.Though known to be explosive, when used carefully this reagent makes methyl esters from carboxyiic acids. Draw it’s other two resonance structures (2 pts) and show curved arrows for the formation of each (2 pts). Be sure to include all lone pair electrons and charges! Circle the greatest contributor (2 pts). (6 pts total) (from 1.74 in the book!) END OF SECTION 2 and Exam 22 ...
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This note was uploaded on 03/20/2011 for the course CHEMISTRY 310m taught by Professor Iverson during the Fall '08 term at University of Texas.

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CH310M-Exam1_KEY[1] - CH 310/318M EXAM 1 Williams— Fall...

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