Organic Chemistry
Organic Chemistry
9th Edition
ISBN: 9781305080485
Author: John E. McMurry
Publisher: Cengage Learning
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Chapter 9.SE, Problem 14VC

Name the following alkynes, and predict the products of their reaction with (1) H2 in the presence of a Lindlar catalyst and (2) H3O+ in the presence of HgSO4:

Chapter 9.SE, Problem 14VC, Name the following alkynes, and predict the products of their reaction with (1) H2 in the presence

Expert Solution
Check Mark
Interpretation Introduction

a)

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  1

Interpretation:

The alkyne shown is to be named and the products formed when it reacts with 1) H2 in the presence of Lindlar catalyst and 2) H3O+ in the presence of HgSO4 is to be predicted.

Concept introduction:

The longest carbon chain which contains the carbon-carbon triple bond is chosen. The chain is numbered from the end that gives the lowest number to the carbon in triple bond. Compounds with more than one triple bond are called diynes, triynes and so forth. The substituents present, if any are written in the alphabetical order.

When reduced with Hydrogen in the presence of Lindlar catalyst the reduction of alkynes stops in the alkene stage. When treated with H3O+ in the presence of HgSO4, alkynes undergo hydration following Markovnikov regiochemistry to give an enols which will tautomerize to yield aldehydes (terminal alkynes) or ketones (internal alkynes).

To give:

The name of the alkyne shown and to predict the products formed when it reacts with 1) H2 in the presence of Lindlar catalyst and 2) H3O+ in the presence of HgSO4.

Answer to Problem 14VC

The name of the alkyne shown is 4,4-dimethyl-1-hexyne.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  2

The product formed when it reacts with H2 in the presence of Lindlar catalyst is 4,4-dimethyl-1-hexene.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  3

The product formed when it reacts with H3O+ in the presence of HgSO4 is 4,4-dimethyl-2-hexanone.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  4

Explanation of Solution

The compound has a six carbon straight chain with two methyl groups on C4 with a triple bond between C1 & C2. Hence it’s name is 4,4-dimethyl-1-hexyne.

When reduced with hydrogen in the presence of Lindlar catalyst, the triple bond becomes a double bond as each of the two carbons in the triple bond gets attached to a hydrogen and an alkene, 4,4-dimethyl-1-hexene,is thus produced.

When treated with H3O+ in the presence of HgSO4, the addition of water takes place in the triple bond following Markovnikov regiochemistry. The OH group adds to more highly substituted carbon and H adds to the less highly substituted carbon in triple bond resulting in the formation of an enol which undergoes tautomerization to yield the ketone, 4,4-dimethyl-2-hexanone.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  5

Conclusion

The name of the alkyne shown is 4,4-dimethyl-1-hexyne.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  6

The product formed when it reacts with H2 in the presence of Lindlar catalyst is 4,4-dimethyl-1-hexene.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  7

The product formed when it reacts with H3O+ in the presence of HgSO4 is 4,4-dimethyl-2-hexanone.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  8

b)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The alkyne shown is to be named and the products formed when it reacts with 1) H2 in the presence of Lindlar catalyst and 2) H3O+ in the presence of HgSO4 is to be predicted.

Concept introduction:

The longest carbon chain which contains the carbon-carbon triple bond is chosen. The chain is numbered from the end that gives the lowest number to the carbon in triple bond. Compounds with more than one triple bond are called diynes, triynes and so forth. The substituents present, if any are written in the alphabetical order.

When reduced with Hydrogen in the presence of Lindlar catalyst the reduction of alkynes stops in the alkene stage. When treated with H3O+ in the presence of HgSO4, alkynes undergo hydration following Markovnikov regiochemistry to give an enols which will tautomerize to yield aldehydes (terminal alkynes) or ketones (internal alkynes).

To give:

The name of the alkyne shown and to predict the products formed when it reacts with 1) H2 in the presence of Lindlar catalyst and 2) H3O+ in the presence of HgSO4.

Answer to Problem 14VC

The name of the alkyne shown is 2,7-dimethyl-4-octyne.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  9

The product formed when it reacts with H2 in the presence of Lindlar catalyst is cis-2,7-dimethyl-4-octene.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  10

The product formed when it reacts with H3O+ in the presence of HgSO4 is 2,7-dimethyl-4-octanone.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  11

Explanation of Solution

The compound has an eight carbon straight chain with two methyl groups on C2 & C7 with a triple bond between C4 & C5. Hence it’s name is 2,7-dimethyl-4-octyne.

When reduced with hydrogen in the presence of Lindlar catalyst, the triple bond becomes a double bond as each of the two carbons in the triple bond gets attached to a hydrogen and an alkene, cis- 2,7-dimethyl-4-octene.is thus produced.

When treated with H3O+ in the presence of HgSO4, the addition of water takes place in the triple bond. As the alkene is symmetrical the Markovnikov regiochemistry cannot be applied. The OH group adds to one carbon and H adds to the other carbon in triple bond resulting in the formation of an enol which undergoes tautomerization to yield the ketone, 2,7-dimethyl-4-octanone.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  12

Conclusion

The name of the alkyne shown is 2,7-dimethyl-4-octyne.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  13

The product formed when it reacts with H2 in the presence of Lindlar catalyst is cis-2,7-dimethyl-4-octene.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  14

The product formed when it reacts with H3O+ in the presence of HgSO4 is 2,7-dimethyl-4-octanone.

Organic Chemistry, Chapter 9.SE, Problem 14VC , additional homework tip  15

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Chapter 9 Solutions

Organic Chemistry

Ch. 9.8 - Prob. 11PCh. 9.9 - Show the terminal alkyne and alkyl halide from...Ch. 9.9 - Beginning with acetylene and any alkyl halide...Ch. 9.SE - Name the following alkynes, and predict the...Ch. 9.SE - From what alkyne might each of the following...Ch. 9.SE - Prob. 16VCCh. 9.SE - The following cycloalkyne is too unstable to...Ch. 9.SE - Prob. 18MPCh. 9.SE - Assuming that strong acids add to alkynes in the...Ch. 9.SE - Prob. 20MPCh. 9.SE - Prob. 21MPCh. 9.SE - Prob. 22MPCh. 9.SE - Prob. 23MPCh. 9.SE - Prob. 24MPCh. 9.SE - Reaction of acetone with D3O+ yields...Ch. 9.SE - Give IUPAC names for the following compounds:Ch. 9.SE - Draw structures corresponding to the following...Ch. 9.SE - Prob. 28APCh. 9.SE - Prob. 29APCh. 9.SE - Prob. 30APCh. 9.SE - Predict the products from reaction of l-hexyne...Ch. 9.SE - Prob. 32APCh. 9.SE - Prob. 33APCh. 9.SE - Propose structures for hydrocarbons that give the...Ch. 9.SE - Identify the reagents a-c in the following scheme:Ch. 9.SE - Prob. 36APCh. 9.SE - Prob. 37APCh. 9.SE - Prob. 38APCh. 9.SE - How would you carry out the following...Ch. 9.SE - Prob. 40APCh. 9.SE - Synthesize the following compounds using 1-butyne...Ch. 9.SE - Prob. 42APCh. 9.SE - Prob. 43APCh. 9.SE - Prob. 44APCh. 9.SE - Prob. 45APCh. 9.SE - A hydrocarbon of unknown structure has the formula...Ch. 9.SE - Compound A(C9H12) absorbed 3 equivalents of H2 on...Ch. 9.SE - Hydrocarbon A has the formula C12H8. It absorbs 8...Ch. 9.SE - Occasionally, a chemist might need to invert the...Ch. 9.SE - Prob. 50APCh. 9.SE - Prob. 51APCh. 9.SE - Prob. 52APCh. 9.SE - Prob. 53APCh. 9.SE - Prob. 54APCh. 9.SE - Prob. 55APCh. 9.SE - Prob. 56APCh. 9.SE - Prob. 57AP
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