Understanding Alkenes & Alkynes: Bromine Water Test

In summary, to distinguish between an Alkene and Alkyne, you can use bromination reactions. Adding excess Br2 to an alkyne results in tetrabromination, while adding excess Br2 to an alkene results in dibromination. By analyzing the number of bromines added through mass or spectroscopy, you can determine if the compound is an alkyne or alkene. Additionally, IR and NMR spectroscopy can also be used to differentiate between the two compounds.
  • #1
Bladibla
358
1
Hey all

How do you distinguish between and Alkene and Alkyne?

Bromine water is discoloured in both, so that rules out BW.
 
Chemistry news on Phys.org
  • #2
you could try to take the compound and try to brominate the bond twice. excess Br2+alkyne---> tetrabromination excess Br2+alkene----->dibromination. So if your compound is an alkyne you can add on 4 bromines, if it is an alkene you can add on 2 bromines. After you are done reacting you can figure out how many bromines were added by finding mass or doing spectroscopy thus you can figure out if the compound is an alkyne or alkene
 
  • #3
How about just getting an IR spectrum? If the alkyne isn't symmetrical, that is.

The alkyne stretching frequency should be significantly different from the alkene stretching frequency.
 
  • #4
NMR would tell you what your compound is as well, you would just have to look for different splitting patters.
 

Related to Understanding Alkenes & Alkynes: Bromine Water Test

1. What is the purpose of the bromine water test?

The bromine water test is used to determine the presence of alkenes and alkynes in a compound. Specifically, it tests for the unsaturation of a compound, meaning the presence of double or triple bonds between carbon atoms.

2. How does the bromine water test work?

The bromine water test is a type of chemical reaction known as an addition reaction. When bromine water, which is a reddish-orange solution of bromine in water, is added to a compound containing a double or triple bond, the bromine molecules break apart and add to the unsaturated carbon atoms, resulting in a colorless solution.

3. What is the difference between the bromine water test for alkenes and alkynes?

The bromine water test for alkenes and alkynes is essentially the same, except for the time it takes for the reaction to occur. Alkenes react faster with bromine water compared to alkynes, which require more time for the addition reaction to take place due to the strength of the triple bond.

4. What are some limitations of the bromine water test?

The bromine water test may not work for compounds that contain other functional groups, such as alcohols or carboxylic acids, as they can also react with bromine water. Additionally, some compounds may not give a clear result due to the presence of impurities or other factors.

5. Can the bromine water test be used to distinguish between alkenes and alkanes?

No, the bromine water test cannot be used to distinguish between alkenes and alkanes. Both types of compounds do not react with bromine water, so the solution will remain reddish-orange regardless of the presence of alkenes or alkanes.

Similar threads

Replies
4
Views
2K
Replies
2
Views
11K
Replies
1
Views
1K
  • Biology and Chemistry Homework Help
Replies
7
Views
1K
  • Chemistry
Replies
3
Views
7K
  • Biology and Chemistry Homework Help
Replies
28
Views
4K
Replies
21
Views
3K
Replies
18
Views
3K
  • Biology and Chemistry Homework Help
Replies
1
Views
997
Back
Top