Organic Chemistry

dhilipan1995's Avatar
Cool goIITian

Joined: 1 Oct 2011
Post: 58
12 Mar 2012 18:15:11 IST
1 People liked this
4
526 View Post
The most dubious doubt i have ??
Engineering Entrance , Medical Entrance , NEET , JEE Main , AIIMS , JEE Main & Advanced , Chemistry , Organic Chemistry

 There is Carbon - Carbon single bond and Carbon - Carbon double bond and Carbon - Carbon triple bond......

To my question ...

Why there is no Carbon - Carbon 4 bond even though Carbon has valency of 4 .

 



Comments (4)

Niladri Chakraborty's Avatar

Hot goIITian

Joined: 21 Feb 2012
Posts: 109
12 Mar 2012 18:50:23 IST
2 people liked this

 

 

Carbon has a valence of four. It can form four bonds but it only forms compounds with single bonds (alkanes) double bonds (alkenes) or triple bonds (alkynes).

Even the alkynes are unstable. Nearby oxygen and nitrogen form common diatomic molecules, but not with quadruple (or even triple) bonds. The basic answer would have to be that once you have the triple bond, there's no possible quantum orbit that allows one more electron to orbit both nuclei such that the total molecule has a lower energy.

For an electron to orbit both nuclei instead of just one, its orbit length would need to be increased by one wavelength of its wavefunction (raising it to a higher energy level), or the nuclei would need to move closer together (increasing the repulsive electrostatic potential energy between them). That repulsion is inverse square with distance, so the closer you push the nuclei together, the harder it is.

There is no space to accommodate that bond. Think of an alkyne like ethyne. Ethyne has 1 sigma bond and 2 pi bonds. What does this mean in 3D? Well picture 2 basket balls (carbon) with a pipe connecting the two of them, this is your sigma bond. Lets say that the sigma bond is on your y-axis, and that the y-axis is in the plane of your paper. Now lets add a pi bond, this pi bond will be on the z-axis (going up and down). Now we have to add the second pi bond, but they only space available is on the x-axis (coming out and goind back in). It is pretty crowded now and we cannot fit another pi bond between the carbons, that is why you will not see a carbon-carbon quadruple bond.  

 

 

Niladri Chakraborty's Avatar

Hot goIITian

Joined: 21 Feb 2012
Posts: 109
12 Mar 2012 18:51:19 IST
0 people liked this

 sorry, the picture didn't come properly.. click here to view it.

dhilipan1995's Avatar

Cool goIITian

Joined: 1 Oct 2011
Posts: 58
12 Mar 2012 19:13:38 IST
0 people liked this

What is the source ??
Niladri Chakraborty's Avatar

Hot goIITian

Joined: 21 Feb 2012
Posts: 109
12 Mar 2012 19:54:20 IST
0 people liked this




Quick Reply


Reply

Some HTML allowed.
Keep your comments above the belt or risk having them deleted.
Signup for a avatar to have your pictures show up by your comment
If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team
Free Sign Up!
Sponsored Ads

Preparing for JEE?

Kickstart your preparation with new improved study material - Books & Online Test Series for JEE 2014/ 2015


@ INR 5,443/-

For Quick Info

Name

Mobile

E-mail

City

Class

Vertical Limit

Top Contributors
All Time This Month Last Week
1. Bipin Dubey
Altitude - 16545 m
Post - 7958
2. Himanshu
Altitude - 10925 m
Post - 3836
3. Hari Shankar
Altitude - 10085 m
Post - 2217
4. edison
Altitude - 10825 m
Post - 7804
5. Sagar Saxena
Altitude - 8635 m
Post - 8064
6. Yagyadutt Mishr..
Altitude - 6330 m
Post - 1958

Find Posts by Topics

Physics

Topics

Mathematics

Chemistry

Biology

Parents Corner

Board

Fun Zone