Chapter 88.1 Name the following compounds: (a)CH3 CH3CHC CH3 CCHCH3

2,5-dimethyl-3-hexyne (b)CH3 HC CCCH3 CH3

3,3-dimethyl-1-butyne (c)H3CHC CHCH CHC CCH3

2,4-octadiene-6-yne (d)H 3C H3CH2CCC H 3C CCH2CH2CH3

3,3-dimethyl-4-octyne (e)H3C H3CH2CCC H3C CH3 CCHCH3

2,5,5-trimethyl-3-heptyne (f)

6-isopropyl-cyclodecyne 8.2 There are seven isomeric alkynes with the formula C6H10. Draw and name them. Solution:

1-Hexyne

2-Hexyne

3-Hexyne

3-methyl-1-pentyne

4-methyl-1-pentyne

4-methyl-2-pentyne

3,3-dimethyl-1-butyne

8.3 What products would you expect from the following reactions? (a)H2 C H3 C C H2

C CH

+

H2 C

ClC H2 C CH

Cl

2Cl 2

H 3C

Cl(b)

Cl

C

CH

+C C

HBr

C

CH2

Br

(c)H2 C H 3C C H2 H2 C

CH3

+

C 4H 9

HBr Br

C

H C

CH3

8.4 What product would you obtain by hydration of the following alkynes?

(a)

hydration C 3H 7 C C C3H 7 C3H 7 C O(b)

H2 C

C3H 7

3HCH3 C CH H2 C

hydration C C C 3H 7H3 C

3HCCH H2 C

C O

C C 3H 7 H2

8.5 What alkynes would you start with to prepare the following ketones?O

O

(a)

CH3CH2CH2CCH3

(b)

CH3CH2CCH2CH3

Solution: (a)

CH3CH2CH2C

CH (b)

CH3CH2C

CCH3

8.6 What alkyne would you start to prepare each of the following compounds by a hydroboration / oxidation reaction?

O CH2 CH

CH3

O

CH3CHCH2CCHCH3(a) Solution:CH C

(b)

CH3

CH3

CH3CHC(a) (b)

CCHCH3 CH3

8.7 How would you prepare the following carbonyl compounds starting from an alkyne?

Br

O

Osolution:Br Br

HgSO4, H3OO

O

1.BH3 2.H2O2 / NaOH8.8 Using any alkyne needed, how would you prepare the following alkenes? (a) trans-2-Octene (b) cis-3-Heptene (c) 3-Methyl-1-pentene solution: (a)

Li,NH3(b)

H2 Lindlar catalyst(c)

H2 Lindlar catalyst

8.9 Propose structures for alkynes that give the following products on oxidative cleavage by KMnO4: (a)CO2H

+

CO2

(b) 2CH3(CH2)7CO2H + HO2C(CH2)7CO2H Solution: The structure is: (a)

(b) CH3(CH2)7CC(CH2)7CC(CH2)7CH3

8.10 The pKa of acetone, CH3COCH3, is 19.3. Which of the following bases is strong enough to deprotonate acetone? (a) KOH (pKa of H2O = 15.7) (c) NaHCO3 (pKa of H2CO3 = 6.4) Solution: (b) Because pKa (C2H2) > pKa (CH3COCH3) 8.11 Show the terminal alkyne and alkyl halide from which the following products can be obtained. If two routes look feasible, list both. Answer: (a)H3CH2 CH2CC H3CH2CH2C CH CH Br

(b) Na+ -CCH (pKa of C2H2 = 25) (d) NaOCH3 (pKa of CH3OH = 15.6)

CH3CH2CH2CH3

C

C

CH3

3HCC

Br

(b)

H3C H3CHC C C CH2CH3CCH3 C

H3C H3CHC C CH

Br

CH2CH3

CH C

BrCH3(c) 8.12 How would you prepare cis-2-butene starting from propyne, an alkyl halide, and any other reagents needed? This problem cant be worked in a single step. Youll have to carry out more than one

reaction. Answer:H3CC CH

NaNH2 NH3 H2

BrCH3 THF HCH3C

H3CC

CCH3

CH CH3

H3CC

CCH3

Lindar catalyst

8.13 Beginning with 4-octyne as your only source of carbon and using any inorganic reagents necessary, how would you synthesize the following compounds? (a) Butanoic acid Solution: (a)O

(b) cis-4-Octene

(c) 4-Bromooctane

(d) 4-Octanol (4-hydroxyoctane)

(e) 4,5-Dichlorooctane

KMnO4 H3O(b)H2 Lindler catalyst

2

OH

(c)H2 Lindler catalyst

HBr, ether

Br

(d)

H2 Lindler catalyst

1.BF3 , THF 2.H2 O2 , OHOH

(e)H2 Lindler catalyst

X2 CH2Cl2Cl

Cl

8.14 Beginning with acetylene and any alkyl halides needed, how would you synthesize the following

compounds? (a) Decane (c) Hexanal Solution: (a) (b) 2,2-Dimethylhexane (d) 2-Heptanone

NaNH2

Na C

CH

CH3 CH2 CH2CH2CH2CH2CH2CH2Br

2H2 Pd/C

(b)

NaNH2

Na C

CH

(CH3)3CCH2CH2Br

2H2 Pd/C

(c)NaNH2 Na CCH

CH3CH2CH2CH2Br 1.BH3 2.H2O2

O

(d)

NaNH2

Na C

CH

CH3CH2CH2CH2CH2Br

H2 SO4, H2O HgSO4

O

8.15 Name the following alkynes, and predict the products of their reaction with (i) H2 in the presence

of a Lindlar catalyst and (ii) H3O+ in the presence of HgSO4:

(a)HC C C H2 H3C C H2C CH3 CH3 H3C

(b)

CH3

HC C H2 C C CH2 CH H3C CH3

Solution:

H

2

/L in dl ar

Ca

t

8.16 From what alkyne might each of the following substances have been made?

(a)CH3 CH H3C C H2 H2 C C H O H2 C

(b)H2 C CH3 H C C H2 Cl C Cl CH3

SO HgH2

i /L

4

rC la nd

/H3

Oat

+

O

H

H2 C C H

O gS4

/H3

O

+

O

Solution: (a) is fromCH3 CH H3C H2C C CHH2 C H2 C CH3 H C C H2

H2 C C H

C

CH

4-Methyl-pentyne

and (b) is from 1-Ethynyl-2-methyl-cyclohexane

8.17 How would you prepare the following substances, starting from any compounds having four

carbons or fewer?HO CH2 C H2

CH

HC C H2

(a)

H3 C

HO H C C H2O H2 C C C H2 H CH3

OH

CH

CH2

Zn(Cu) Ether H 3C

CH C H2

HC

CH2 C H2

Solution:

H3C

H2C

C

(b)

O H2 C C C H2 H CH

H2SO4, H2O HgSO4 H2CC

H2 C C H2 H

C CH3

H2C

C

Solution:

8.18 The following cycloalkyne is too unstable to exist. Explain.

H2C C H2

CH2

Solution: Its not possible to form a small ring containing a triple bond because the angle strain that would result from bending the bonds of an SP-hybridized carbon to form a small ring is too great.8.19 Give IUPAC names for the following compounds. CH3

CH3 CH2Ca. b.

CCCH3 CH3

CH3C

CCH2CCH3

CCH2CH3CH3

c. CH3CH

CC

CCHCH3

CH3

HCd. e. H2 C

CCCH2C CH3CHCH

CH

CHC

CH

CH2CH3

CH3CH2 CHCf. Solution:CH2CH3

CCHCHCH3 CH3

a. 2,2-Dimethyl-3-hexyne b. 2,5-Octadiyne c. 3,6-Dimethyl-2-heptene-4-yne d. 3,3-Dimethyl-1,5-hexadiyne e. 1,3-Hexadiene-5-yne f. 3,6-Diethyl-2-methyl-4-octyne8.20 Draw structures corresponding to the following names:

a. 3,3-Dimethyl-4-octyne b. 3-Ethyl-5-methyl-1,6,8-decatriyne c. 2,2,5,5-Tetramethyl-3-hexyne d. 3,4-Dimethylcyclodecyne e. 3,5-Heptadien-1-yne f. 3-Chloro-4,4-dimethyl-1-nonen-6-yne g. 3-sec-Butyl-1-heptyne h. 5-tert-Butyl-2-methyl-3-octyne

Solution:

a.

3,3-Dimethyl-4-octyne

b.

3-Ethyl-5-methyl-1,6,8-decatriyne

c. 3,6-Dimethyl-2-heptene-4-yne

d. 3,4-Dimethylcyclodecyne

e.

3,5-Heptadien-1-yne

Cl

f.

3-Chloro-4,4-dimethyl-1-nonen-6-yne

g.

3-sec-Butyl-1-heptyne

h. 5-tert-Butyl-2-methyl-3-octyne8.21 The following two hydrocarbons have been isolated from various plants in the sunflower family.

Name them according to IUPAC rules. (a)H3C C H C H C C C C C H C H C H C H C H CH2

(b)H3C C C C C C C C C C C C H CH2

SOLUTION: (a) (b) (3E, 5E, 11E)-1,3,5,11-Tridecatetraen-7, 9-diyne. 1-Tridecene-3, 5, 7, 9, 11-pentayne

8.22. Predict the products of the following reactions.H

H2, Pd/C

A

H2/LindlarSOLUTION: A:H2 C C H2 H2 C CH3

B

B:

H C C H

H C CH2

8.23 A hydrocarbon of unknown structure has the formula C8H10. On catalytic hydrogenation over the

Lindlar catalyst, 1 equivalent of H2 is absorbed. On hydrogenation over a palladium catalyst, 3 equivalents of H2 are absorbed. a) How many degrees of unsaturation are present in the unknown? b) How many triple bonds are present? c) How many double bonds are present? d) How many rings are present? e) Draw a structure that fits the data. Solution: a) c) e) 4 degrees of unsaturation are present. 1 double bond is present. The possible structure can be: b) 1 triple bond is present. d) 1 ring is present.

etc...8.24 Predict the products from reaction of 1-hexyne with the following reagents:

a) 1 equiv HBr c) H2, Lindlare catalyst e) H2O, H2SO4, HgSO4 Solution:

b) 1 equiv Cl2 d) NaNH2, in NH3, the CH3Br f)2 equiv HClHCl

a)

1-hexyneCl2

ClCl

b)

1-hexyneH2 Lindlar Catalyst

Cl

H

c)

1-hexyne

H

H

NaNH2

CNa

CH3Br

d)

1-hexyne

NH3

O

H2SO4,H2O HgSO4

e)

1-hexyneCl

2HCl

f)

1-hexyne

Cl

8.25 Predict the products from reaction of 5-decyne with the following reagents:

(a) H2, Lindlar catalyst. (b) Li in NH3. (c) 1 equiv Br2. (d) BH3 in THF, then H2O2, OH-. (e) H2O, H2SO4, HgSO4. (f) Excess H2, Pd/C catalyst. Solution:H H H C4H9 Br C4H9

O

(a)

C4H9 C4H9

C4H9. O

(b)

C4H9

H

. (c)

C4H9

Br

. (d)

C4H9

C4H9.

C4H9

(e)

C4H9.

(f)

C4H9

8.26 Predict the products from reaction of 2-hexyne with following reagents:

(a) 2 equ