Alcoholic $KOH$ at $200^\\circ C$

Treat with alcoholic $KOH$ at $200^\\circ C$ to eliminate two equivalents of $HBr$

Question 1

Which of the following statements best describes the geometry of alkynes?

Accepted Answer

Alkynes have a linear geometry around the triple bond.

Question 2

What is the molecular formula for a noncyclic alkyne with 5 carbon atoms?

Accepted Answer

$C_5H_8$

Question 3

Which of the following best explains why triple bonds are shorter than double or single bonds?

Accepted Answer

Triple bonds have two pi overlapping orbitals, which increases electron density between nuclei.

Question 4

Which of the following is the correct IUPAC name for the compound $CH_3C \equiv CCH_2CH_3$?

Accepted Answer

2-pentyne

Question 5

Terminal alkynes are more acidic than other hydrocarbons due to:

Accepted Answer

The higher p character of the sp hybridized carbon.

Question 6

Which reagent is commonly used to convert a terminal alkyne to an acetylide ion?

Accepted Answer

$NaNH_2$

Question 7

What is the product when an acetylide ion reacts with a primary alkyl halide?

Accepted Answer

A substituted alkyne

Question 8

Which of the following conditions favors the formation of an internal alkyne during elimination reactions?

Accepted Answer

Alcoholic $KOH$ at $200^\circ C$

Question 9

Partial hydrogenation of alkynes using Lindlar's catalyst produces:

Accepted Answer

A cis alkene

Question 10

Which method will convert an alkyne to a trans alkene?

Accepted Answer

Reduction with sodium in liquid ammonia ($Na/NH_3$)

Question 11

When $Br_2$ is added to an alkyne, what is the major product if two equivalents are used?

Accepted Answer

A tetrahalide

Question 12

The addition of $HX$ to an alkyne follows Markovnikov's rule. What is the major product when $HBr$ is added to 1-butyne?

Accepted Answer

2,2-dibromobutane

Question 13

Which reagent will result in anti-Markovnikov addition of $HBr$ to a terminal alkyne?

Accepted Answer

Peroxide ($ROOR$)

Question 14

Hydration of a terminal alkyne with $HgSO_4$ and $H_2SO_4$ produces:

Accepted Answer

A methyl ketone

Question 15

What is the intermediate formed during acid-catalyzed hydration of alkynes?

Accepted Answer

Vinyl cation

Question 16

Hydroboration-oxidation of a terminal alkyne produces which functional group?

Accepted Answer

An aldehyde

Question 17

Which reagent is used in the hydroboration-oxidation of alkynes?

Accepted Answer

Disiamylborane

Question 18

Oxidation of alkynes with warm, basic $KMnO_4$ produces:

Accepted Answer

Two carboxylic acids

Question 19

Ozonolysis of an alkyne will produce which type of compound?

Accepted Answer

Carboxylic acids

Question 20

Which synthetic pathway would you use to convert 1-bromopentane to 1-pentyne?

Accepted Answer

Treat with alcoholic $KOH$ at $200^\circ C$ to eliminate two equivalents of $HBr$

Comprehensive Study Notes: Reactions and Properties of Alkynes

Study Guide - Practice Questions