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7) If a reaction is exothermic, then a) ?S<0 b) ?S>0 c) ?H<0 d) ?H>0 9 ) What te

ID: 793286 • Letter: 7

Question

           

  7) If a reaction is exothermic, then

            a) ?S<0           b) ?S>0           c) ?H<0          d) ?H>0

9) What term describes the structural relationship between (2R,3R,4S)-2,3,4-trichloroheptane and (2S,3S,5R)-2,3,5-trichloroheptane?

a) not isomers         b) constitutional isomers         c) enantiomers         d) diastereomers

   10) Which would rotate a plane of polarized light?

a) an achiral compound       b) a meso compound       c) an equimolar mixture of enantiomers

d) an equimolar mixture of diastereomers


   12) What type of intermediate is present in the SN2 reaction of cyanide with bromoethane?

a) carbocation         b) free radical         c) carbine         d) carbanion

e) This reaction has no intermediate.

  

   13) Which of these compounds has a meso form?

a) 2,3-dibromobutane        b) 1,3-dibromobutane        c) 1,2-dichlorobutane     

d) 1,4-dibromobutane        e) 1-bromo-2-chlorobutane

   14) Which of these is the rate law for an SN2 reaction?

            a) rate = k[alkyl halide]                                   b) rate = k[nucleophile]

            c) rate = k[alkyl halide][nucleophile]              d) rate = k[alkyl halide][nucleophile]2

15) In the first propagation step of the free radical chlorination of methane, which of the following occurs?

a) Cl2 dissociates                                b) A chlorine radical abstracts a hydrogen

c) A carbon radical reacts with Cl2     d) A carbon radical reacts with a chlorine radical

e) Two chlorine radicals combine

   16) In the reaction between methane and chlorine, which of the following compounds cannot be      

    formed through a termination reaction?

a) CH3Cl         b) HCl         c) CH3CH3         d) Cl2

  

   17) Which of the following reactive intermediates can best be described as both nucleophilic and   

   strongly basic?

a) carbanions         b) carbocations         c) carbenes         d) free radicals         e) alkanes

   18) Which of the following reactive intermediate species maintains sp3 hybridization?

a) methyl carbanion                b) dibromocarbene         c) tertiary carbocation

d) secondary alkyl radical       e) both B and C

   19) Which of the following solvents could be described as polar and protic?

         a) ethanol         b) acetonitrile         c) dimethylformamide         d) acetone

   20) Which of the following alkyl chlorides will undergo SN1 reaction most readily?

         a) 1-chloro-4-methylpentane                             b) 2-chloro-4-methylpentane

         c) 2-chloro-3-methylpentane                 d) 2-chloro-2-methylpentane

Explanation / Answer

1.a) ?S<0


2.c) enantiomers


3.
a) an achiral compound

4.e) This reaction has no intermediate.

5.
6.a) rate = k[alkyl halide]

7.

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