C357_Exam_1_Key_2005 - Cornell University Chemistry 357...

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Unformatted text preview: Cornell University Chemistry 357 Summer 2005 Examination 1 June 13, 2005 Instructions: Read all questions completely before answering. If the question is still unclear, be sure to ask for clarification. You may find it helpful to first answer those questions that you find easier and then return to those you find more difficult. Good Luck! !! Name: Signature: (/ijl/ Page 1 of 9 1) (XX pts) Provide an IUPAC name for each of the structures shown below and write your answer on the line to the right of the structure. Or‘ when given a name, draw the appropriate structure on the line. Be sure to include any required stereochemical designations. J A) .7 fl ,. V ‘ my] L; "L IQ, Lflmgl‘f,7} ?’+c+lilmgfitr{(:‘/‘CTEUOLB B) C) D) 2,2,3—trimethylpentane E) 3‘6-di ethyl~2,4,4,7—tetramethyloctane CH’ ".x I?) Dicyclohexylmethane Page 2 of 9 2) (XX pts) For each of the indicated pair of bonds in the molecule of Pepcid below (indicated by arrows with matching letters): write “shorter” at the end of the arrow pointing to the shorter bond of the two of each pair (A through E). If the bonds are the same length, write “same” at the end of either arrow of the pair. 3) (XX pts) Circle the following compound of each pair that you would expect to have a higher boiling point. ow mw® Page 3 of 9 4) (XX pts) For each of the following cyclohexane structures, draw and circle each in its most stable conformation. If both chairs are of equal stability, draw both and circle both. Answers that are not circled will be graded as the least stable(l) even if they are the only Structure you have drawn‘tsor circle your choice for most stable!). "luncnzcu3 H3CH2 Page 4 of 9 5) (XX pts) For each of the molecules shown below; draw a Newman projection (single- eyed if one bond is indicated (by the arrow and eye) or double eyed if two bonds are indicated (by the arrows and double eyes» looking down the bond, in the direction indicated and in the exact conformation drawn below! Models may help you! CH3 H , , A) 6%. \ Cl-I~ H C D) J 3 H 4—).— CH2C1~I3 H3C H Page 5 of 9 6) (M'pts) Using the numbers 1. 2, and 3. rank each of the following sets of bonds in terms of increasing polarity (l = most polar. 3 =least polar). Write your answer on the line below each bond. A) C—l-l 0—H N—H B) C—H 3—“ 0—H 3 I T71 a J. _.__. D) c—o C—N C—C (fill _1_a_3_ 7) (XX pts) Describe the relationship of each of the pairs of compounds shown below. Write your answer on the line below each pair. Cl Cl/l .‘ O 0- A) i > B) A A I NH3 \ NL 1-1 c1 | H (SCKWLQ (Eggs/1mm e {3024/ rs. 1-1 0/ 0 ~SOWVKQ Shy/U Chrch l S Comte/5 (5W {If} Page 6 of 9 8) (XXpts) Do the Sp2 hybridized carbons and the indicated atoms have to lie in the same Plane. Write “yes” at the end of the arrow if that atom must be in the same plane as the Sp“ hybridized carbons and write “no” at the end of the arrow if it is possible for the atom to not he in the plane of the sp2 hybridized carbons. Vb [\Jo H H H 1H \d H . “ H>C H H’ H __ B) H A) . 1-1 ,,c/—H H C.,H<———l\)b / ,C\ \H I \ H H O /'H H (‘67 /N() i H H H \Cl‘/ [RX] U , ($5 —‘—’ H . C) / " H Page 7 of 9 10) (XX pts) Calculate the formal charge on each of the indicated atoms in the following structure and write your answer on the line at the end of the arrow. ( «H .— B) 11) (XX pts) For each of the following pairs of structures, circle the one which you believe is the more stable resonance form. If both are of equal stability, circle both structures. Page 8 of 9 12) (XXpts) Please determine the hybridization of the indicated atoms and write your answer on the line at the end of each arrow. :7 [3‘7 x “h «it? fit A.) z B) l \ C) / “ 7r ‘ . \ 5 / 5/” s F” 9: (so out inn/l wWei‘T‘llg n i— L" i ‘ H brick “MW” E” 1&7 E) \ i B 1‘) ii—CE/N O / ‘ / S /” [\4r 0/ 500‘ 53 Ag CH3 ' 13) (XX pts) Histicline, a commonly occurring amino acid, has the structure shown below. Histidine can react as an acid or a base under proper conditions. First, circle and label the most acidic proton in the molecule and explain, using resonance structures, why this proton is acidic. Second, circle and label the most basic lone pair on the molecule and offer a possible explanation for why it is the most basic lone pair. 0 .0 . U r1sz CH—ii—@ (C féwcrye fl&(/ “0 (—2 (IJH2 ' ’/ 0C7 / 241:0 \ [Esq/ma/MCQ; .. Ar \_ MW yaw Ne . $(C V \ r Witt/LL / (674:; r j 0:4 (seem OWE/i" , a a in 1/1; ' .> M2" L - Vi (V, V {dc/V W/CflWL/R / I / .2 I t k ‘ i'Mm/L x gq/ I c l "i 360' U Page 9 of 9 14) (XX pts) For each of the compounds shown below, draw all of the possible resonance forms for each and Show electron “movement” with proper an‘ows. C) ...
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