Unformatted text preview: Organic Chemistry CH231 October 2002
First Examination (l0) 1.Write resonance structures for the following: (a) formate ion, HCO2’ (b) formaldehyde. H200.
and (c) nitrite ion, NOQ’ . Note : atomic numbers , 0:6 , O: 8, and N: 7 . 2. State whether the following reactions have a positive or negative change in entropy , and explain
your choice. . H +CH(‘H=CH
(ﬂ “" 2 3 2 ———-> (‘H3(H2(‘lh 0” <] ———> CH3CH =CH2 (c)('H3(‘()2(aq) + H,o*(aq) ————> (‘H,(Y)2H +H2() 3. Give the order of each of the following reactions
U0) (a)H2 +|2 = 2HI; rate =k(H9(|2)
(b)CHCl3 + Br2 = CBrC13 + HBr ; rate = k (CHCI3 )(Br2)1’2
4.Write structures for the following compounds : (a) 3-chloro bicyclo [ 2.2.1 ] heptane (b) 3-chloro- (I g) 2-methylhexane (c)2,3,4-trimethylpentane (d)trans1.2-difluorocyclobutane (e) 4-(1-methylethyl)
heptane 5. Indicate with an equation how one could convert the following:
‘) mumi )EHn 4——> ((7H,)2CHI)
., 1 (blimthylacclylcnc __'__.> CHJCDZCDJ gC’H’ ‘ -J:
6. The reaction CH4 + Cl . = CH3 . + HCl has an activation enthalpy (AH ) of + 4 Kcal/mol
a 0) and a ( A He) of + 2 Kcal/mol. Draw an energy proﬁle diagram for the reaction. Cf) 7. Draw structures for the two chair conformations of trans - and cis - 1,3 dimethylcyclohexane.
‘ 8. (a) Calculate the specific rotation of a compound, if a solution containing 0.75 grams/ tomL is placed
K 03 in a 1 dm polarimeter tube and its observed rotation at 25 degrees C (D line) is + 1.2 degrees ,
(b) What is the specific rotation of the enantiomer ?
9. Assign R and S designations to the following compounds: 3 (a) B (b) (c)
Q5 s4 it! a Hozcrcdg “TB' l s H Br
Cl ‘ 10. How many stereo isomers can be obtained from the hydrogenation of both double bonds of
(‘0) following compound. Draw the structures . (‘H2 HZC ...
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