CHAPTER 10 HW: ALKENES - Chemistry 21nicholschem.weebly.com/.../1/2/4/9/12497207/21_ch10_hw.pdfPage 1 CHAPTER 10 HW: ALKENES CIS-TRANS AND EZ ISOMERISM 1.!Classify each structure as

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CHAPTER 10 HW: ALKENES

CIS-TRANS AND EZ ISOMERISM

1.   Classify each structure as either cis, trans, E, or Z. Then beside each, draw the related stereoisomer (e.g. if the E isomer is shown, draw the Z isomer).

Structure and

Stereoisomer

cis, trans, E, or Z ?

Structure and

Stereoisomer

cis, trans, E, or Z ?

Structure and

Stereoisomer

cis, trans, E, or Z ?

2.   Draw the following:

a.   Z-2-bromo-4-methyl-2-pentene b. Two stereoisomers of C5H10 c.   Two structural isomers of C5H10

BrBr

CH3

Cl

HO

OH

O H

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3.   Give the IUPAC name for each compound, including cis/trans, R/S, or E/Z stereochemistry where necessary.

Structure

Name

Structure

Name

Structure

Name

ALKENE REACTION WITH HX

4.   Give the curved arrow mechanism for the following reactions. In your mechanisms, include all lone pairs and formal charge.

CH3

OHOH

ClCl

a. H3CC

C

H

H

H

HClH3C

CC

H

H

H Cl

H

b. HBrBr

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5.   For the following reaction,

a.   Draw the curved arrow mechanism that shows formation of both products.

b.   Draw the energy diagram for each reaction (both pathways superimposed on one diagram, or side-by-side to relative scale).

c.   Identify the major product and explain why it is favored over the other product.

6.   Explain which is expected to be the major product in this reaction. Use an energy diagram with your explanation.

HII

I+

HClCl

+

Cl

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7.   In this reaction, both DH˚ and DS˚ are negative. Explain.

8.   Give the curved arrow mechanism for these reactions.

9.   Explain why the major product in this reaction is Q, not R.

HCl Cl

a. HClCl

b. HII

HBrBr

Br+

Q R

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10.  Explain why two products are formed in this reaction.

HYDRATION

11.  For the following reaction,

a.   Give the curved arrow mechanism for the reaction, showing formation of both products.

b.   Explain which is the major product, and use a complete energy diagram with your explanation.

HI

ICH3 CH3I+

OH

OH +H2SO4H2O

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12.  Using the mechanism from the previous problem, explain if acid is catalytic or not in the hydration reaction. [Note: “acid” considers all strong acid forms such as H2SO4 and H3O+.]

13.  Give the curved arrow mechanism for each reaction.

a.H2SO4H2O OH

b. OHH2SO4H2O O

c.H2SO4H2O

OH

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SUMMARY OF ALKENE REACTIONS

14.  Give the major organic product for the following reactions. If a racemic mixture is expected, draw both products. If a rearrangement is probable, give the product from the rearrangement.

HALOGENATION

15.  Give the curved arrow mechanism for each reaction. Include all lone pairs and formal charge.

a. b.HBr HCl

c. d.excess

HI

H2SO4H2O

e.H2SO4H2O

a. Br2Br

Br (racemic)

b.Cl2

Cl

Cl

(racemic)

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16.  Explain why the “anti” addition product is formed in this reaction and not the “syn” product.

17.  Explain why a rearrangement occurs is reaction (1), but not reaction (2).

18.  Molecules X and Y both have a formula of C5H10. Propose a structure of X and Y that is consistent with the observations noted upon addition with a solution of Br2.

Br2

Br

Br

Br

Brnot

anti syn

Br2

HBr

Br

Br

Br(1)

(2)

X Y

2 drops

Br2 in CCl4

2 drops

Br2 in CCl4

Colorless solution

Orange solution

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HALOHYDRIN FORMATION

19.  Give the curved arrow mechanism for each reaction.

20.  Explain the following: a.   The nucleophile mostly attacks the bromonium ion at position X, not position Y.

b.   Two products are formed in equal amounts in this reaction.

a.Cl2H2O

Cl

OH

racemic

b.Br2

CH3OHBr

OCH3

racemic

Br

CH3X

Y

Br2

H2OBr Br+

OH OH

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21.  Which is the expected major product from this reaction? (All are racemic.)

22.  Give the major organic product of each reaction. Indicate if a racemic mixture is expected.

SUMMARY OF ALKENE REACTIONS

23.  Fill in the boxes with the correct reagent(s) for each reaction.

Cl2Cl Cl

CH3OH CH3 OCH3OCH3 CH3

C D

Cl Cl

CH3 ClCl CH3

A B

a. Br2 b.Br2H2O

c.Br2

CH3OHd.

a. Br2, H2O

b. NaH

e.Cl2

OH

f.a. Cl2, H2O

b. NaH

a. b.Br

Cl

Cl

(rac.)

c. d.Br

OH

Cl

CH3O

(rac.)(rac.)

e. f.OH

BrCH3Br

(rac.)

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HYDROBORATION-OXIDATION

24.  Explain the following features of the hydroboration reaction below.

a.   Three moles of alkene react with each mole of BH3.

b.   The reaction is “regioselective.” (Explain why it is regioselective.)

c.   The reaction is “stereoselective.” (Explain why it is stereoselective.)

25.  Give the major organic product for each reaction, paying attention to stereochemistry (syn/anti). Indicate if a racemic mixture is expected.

26.  Fill in the boxes with the correct reagents for each reaction.

a. BH3

OH

CH3

3 b. 3 H2O2, 3 OH- 3(rac.)

a. b.a. BH3

b. H2O2, OH-

a. BH3

b. H2O2, OH-

c. d.a. BH3

b. H2O2, OH-

a. BH3

b. H2O2, OH-

OHa. b.

OH

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SUMMARY OF ALKENE REACTIONS

27.  Give the major organic product(s) of each reaction. Pay attention to stereochemistry and indicate if a racemic mixture is formed. If a rearrangement is probable, give the product from the rearrangement.

SYNTHESIS

28.  Devise a synthesis that can transform each starting material into the product shown. Show all synthetic intermediates and reagents. More than one step is needed in each synthesis.

a. Br2OCH3

b. HCl

c.a. BH3

b. H2O2, OH-d.

H2SO4

O H2O

e.Cl2

OH

a.Br Br

Br (rac.)

b.Cl Br

OH

(rac.)

c.OH

OCH3

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TREE DIAGRAMS FOR 1H NMR SPECTRA

29.  Draw a tree diagram to show the expected splitting for the indicated hydrogen atom in each molecule. Then describe the splitting pattern (e.g. doublet of doublets).

Jab= 2 Hz; Jbc= 7 Hz

Jab= 16 Hz; Jbc= 8 Hz

ALKENE NMR

30.  How many signals should ideally be present in the 1H NMR spectrum of each compound (how many different hydrogen environments are present)? Use labels (a,b,c...) to show which hydrogen atoms should be grouped together.

31.  Assign the 1H NMR spectrum to hydrogen atoms in the structure. Pay attention to splitting + relative

J’s.

Cl

Hb

Cl

Cl HaOH

Hc Hc

Ha

CH3

Hb

cH3C

O

N

Ha. O

CH3b. N

Hc.

NH2

01234567PPM

1H, dd 1H, dd 1H, dd 2H, sa b c d

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32.  Determine a structure that matches the molecular formula and 1H NMR spectrum for each problem. Then assign all peaks in the 1H NMR spectrum to hydrogen atoms in the structure.

0123456789PPM

1H 1H

3H, s

2H, d3H, m

C10H10O

01234567PPM

6H, d

3H, d

1H, m1H, d1H, mJ = 10.2 Hz

C7H12O2Note: J < 2 Hz are not included in the splitting

0246810PPM

1H, s

1H, dd 1H, dd 1H, dd

2H, q

3H, tC4H9N