Fall 09 Exam 2 Chapters 5-8 100points Name If you do not want your graded exam placed in the box outside my office, then please check here Answer all the questions. 1-15 are True / False (15pts) 1) An object is chiral if it has a non-superimposable mirror image. 2) The bond dissociation energy is the amount of energy required to break a bond homolytically. 3) E1 reactions are stereospecific because the leaving group must attack from directly behind the cation. 4) SN2 and E2 reactions always involve a carbocation intermediate. 5) An addition is a reaction where two atoms or groups are removed to produce a new π bond. 6) Alkyl groups are good leaving groups for nucleophilic substitutions. 7) These compounds are enantiomers.

F

Br CH3

HH

Br FCH3

8) A nucleophilic substitution is a reaction where a nucleophilic species replaces another group or atom in a molecule. 9) π bonds are weaker than σ bonds. 10) π bonded electrons are above and below the internuclear axis. 11) SN1 reactions always proceed through a cationic intermediate.

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12) Markovnikov’s rule states that the major product from a substitution will

3) Hammond and Postulate are two of the inventors of the convention for

a C=C double bond.

5) H2O is a stronger base than -OH.

6) (6pts) Assign (R) or (S) to all the chiral centers in the following

7) (2pts) Name an everyday object which is chiral (Your answer cannot be n item of clothing or a body part).

pound in IUPAC form.

OH

be the more highly chiral π bond. 1assigning priority. 14) A C-C single bond is shorter than 1 1molecules.

1a

18) (5pts) Name this com

F CH3Cl

CF3

BrHClCl

CF3

F

H

(a)

(b)

(c) F

F

O

Br

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19) (10pts) For each threesome of molecules, circle the one which will undergo SN1 type reactions the quickest.

Br(a)

(b)

Br

Cl

(c)

(d)

FCH2F(e)

Br

Br

CH3

CH2F

Br

F

Br

Cl Cl Cl

20) (6pts) Draw two isomers of 1,2-dibromo-1-ethylcyclopentane.

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22) Write a mechanism (i.e. curly arrows) for this E2 elimination. (6pts)

K+-OCH3, CH3OHBr

23) (2pts) Draw another possible elimination product which could be formed in small amounts in this reaction. 24) (7pts) Draw and label an Energy Level Diagram for a typical SN1 reaction which is slightly exothermic.

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25) (18pts) Write above the arrow the reagents to use for each of the following transformations.

H

CH3CH2

CH3

CH3CH3CH2

H

CH3

CH3

OH

H(d)

H

CH3CH2

CH3

CH3CH3CH2

HO

CH3

CH3

H

H(c)

H

H3C

CH2CH3

CH2CH3H3C

H

CH2CH3

CH2CH3

Br

H(a)

H

H3C

CH2CH3

CH2CH3H3C

Br

CH2CH3

CH2CH3

H

H(b)

(e)

OH

(f)

HO

O

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26) (10pts) Write the mechanism for (25) part (a) 27) (4pts) Draw the alkene which would react with Chlorine (Cl2) to generate this product.

Cl

ClH

H

CH3

CH3

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Up to 3 Bonus Points

Explain why Sulfoxides (such as CH3SOCH2CH3) are chiral.

CH3 S

O

CH2CH3

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