First Practice Exam CHBM Organic Chemistry I Prof. Bastin Summer 20ll

Transcription

1 First Practice Exam CBM Organic Chemistry Prof. Bastin Summer 20ll Name Provide clear, concise answers using unambiquous, carefully drawn structures (where appropriate) for all of the questions. Good luck and enjoy! 1) /12 pts 2) 110 pts 3) 110 pts 4) /8 pts 5) 110 pts 6) /6 pts 7) 12 pts 8) /6 pts l 9) 110 pts 10) /10 pts 11),./6pts 12) /6 pts 13) /4 pts

2 Bastin - Exam # Fall2010 1) (12 pts) hovide Lewis structures for the following molecules indicating all lone pairs and formal charges (if any). Be sure to show the 3-D structure of the overall molecule. a) C3O F c r-'i-.q,,' t+ F c r+.*r-,p;. R c) TCCCC2 N _/ / ' - b) cro- C:C- /N ' 2) GO ptl) Phosgene, ClrC=O, has a smaller dipole moment than formaldehyde, 'C=O, even though it contains electronegative chlorine atoms in place of hydrogen atoms. Explain. D^ $+ /c*s c1 c- h,rq -!t t{ a QD"c L-cr b""5 q^ o1 =N surn eal r -qr ofil*y N1u< Y te*cn1 -C.. (>ery..rs. 9130t2010 '.q. 1ttene c* t t*<-*- -sn 6L Cqe<q-St*, l-" 6$qr-N Alpe 2

3 Bastin - Exam #l Fall2010 3) (10 pts) Cyclopentadienyl cation is an unusually stable molecule despite each atom NOT having an octet. Explain this unusual stability. Be sure to include words and ALL relevant structures in your explanation. n ---c/i)a l,zc-c --- Yh= + r s-nr.* t esne f.t" L.N.!=s*. 1 r 4) (8 pts) ndicate the hybridization of each non-hydrogen atom in the following molecule. Also, indicate the orbitals that are overlapping to form each bond. 9t30t20t0 -*t' O -srt q -1t' {o ttlll -c:c-c-5c - J 3',1 C,-l C) -t* C,-co ca-ca ct- D.t (r-6c, cs -s t'j.-'!f-t tttrrt s -bx1 - _cn -t t -bb tt' -*{t.rt-t $.,bv{ -n t-u.. '{-*tt {-' :

4 Bastin - Exam # Fal ) (10 pts) Locate (circle) and identify (place name near appropriate circle) the functional groups in the following molecules. acj^j Testosterone (anabolic steriod hormone) $ bf AA Ceclor (common antibiotic) cc^rpar* q qc ) 6) (6 pts) hovide structures for the following compounds. 2 2 #trimethylhexane (b) (R)-3-methylhexane.? (c) cis-p-diethylcyclobutane 9t30t20r0 **-n. n 4

5 Bastin - Exam #l Fall2010 7) (2 pts) Rewrite the following structure using line-angle formulas. c2c3?r. c3c2ccc2cc3 c(c3)2 8) (6 pts) hovide either commonor UPAC names for the following compounds. r 7: Jv..s,s - -Esf -3-*-.+ cya$^atsane 'i '.1 (b) (c) B'; D>C<C3, d2c2cl ti - ) -uryo -q-...oroc^ser c(c3)2 5 -ar",,- )--n"e"- -1.4*{r Y.'q " hc 9t30t20r0

6 Bastin - Exam # FaU ) ( 10 pts) Draw the molecular orbital diagrams for each of the bonds in formaldehyde (structure shown below) using hybrid orbitals. Your MO diagram should include the following information. Please be sure to ask if you have a question. Clear pictures of the hybrid orbitals you are using to construct the MOs. (b) Pictures of the molecular orbitals for each bond. (c) The relative energy of the orbitals. (d) The appropriate number of electrons in the orbitals, being careful to indicate the spin quantum number for each electron (use a little arrow to show spin). e L C- t"j t C - o -o).[ C-o. >"*r,? / 3 vto r*^r^^l C-F ".r C c - t =3 'n- < (@ ot C-o s-bu.'' e ( r,41 c-o (.- 6A 5 q'@-l1 ( L6. o q' C-o "( *o-...{, c ),^, q -Y -Lt 0 ( c^o 4 tw.*o ( "r,_ )( / ( t0 11 lt// ( tlr A,o. 'l 6 9V t )-L' Ufi

7 Bastin - Exam # Fall 2010 l0)(10 pts) Given that a Me-Me eclipsing interaction costs 2.5kcallmol, a Me- eclipsing interaction costs l.4kcallmol, a - eclipsing interaction costs 0.9 kcal/mol, a Et- eclipsing interaction cost 1.5 kcal/mol, a Et-Me eclipsing interaction cost 2.7 kcallmol, a Me-Et gauche interaction costs 1.0 kcal/mol, and a Me-Me gauche interaction costs 0.9 kcal/mol, draw an energy versus dihedral angle plot for the conformations of 3- methylpentane about the C243 bond. Fv l!. hr A e= rfi"ut k ; -[L :-,t')gtt '* p,j<)lu ftuaaer.- -- t+ l+ ' rr L 'l -l - Fc E+ o" Lro" )o' Lt o" O" =(J.1 t.t*o.q)y{,, : go%, 0,,J = (r =.o F'Y"-r ")r'-y; ).J : td il.{d 3o" [rqt.s*.*'-l, : {st'x,, = [o,q]-f,,,^- o.qu'{r, -- tj.s r o.q +.s =- 1.qts"Y",, =Los*fb{,r - -1['{' rl ll v-- A - t lz - -Y 5rYt, ;- -.,. t - + 3oo" a- :-- lt 'l tr( rtt A--- )"to. Dbo 9t30t2010

8 Bastin - Exam # Fall 2010 l l) (6 Pts) What is the relationship (enantiomers, diastereomers, identical/homomers) of the following sets of compounds? Also indicate whether each molecule is chiral or achiral. Assume the molecules arefrozen in the given conformations. (b) FYc3 cl ci Cg Yo C2C3 CU..t E ircl cg d^-,, oyc2c3 cs c"j!"s:.j Q A.^)a,srr (c) cltl cl Fnl cl Q N", N.t"t", t c. rj 4," l, 12)(6 pts) Provide all of the symmetry operations (rotation axes, mirror planes, and inversion centers) present in each of the following molecules. Assume the molecules are"frozen" in the conformations shown. 7 $ (b) (e t^;*";-:.d"- ) c -. h'.;'rh C^5-ct b'"!' ) F'.,' -r Q.lt 3.(rn 9t30t2010

9 Bastin - Exam # Fall 2010 L3)(4 pts) Provide the absolute configuration (rrl,s) of each stereogenicenter in each of the following molecules.,,:s:"'s Br lrrr (b) ) 92C3 n :,_1 V n>c{br T -, c, ) (d) t /''t'bl!"", 3 9t30t20r0