# Homework Help: C-F bond length

1. May 9, 2014

### utkarshakash

1. The problem statement, all variables and given/known data
Choose correct order of C-F bond length
A)C-HF2<C-H2F<C-F3
B)C-F3<C-HF2<C-H2F
C)C-F3<C-H2F<C-HF3
D)C-HF2<C-F3<C-H2F

3. The attempt at a solution

What factors should I look for while measuring bond lengths?

Last edited: May 9, 2014
2. May 9, 2014

### AGNuke

You can take Lone Pair-Bond pair repulsions, Interaction of H and F (due to their size difference), F F interactions, and probably C-H C-F Bond interaction.

3. May 9, 2014

### utkarshakash

Can you please show through an example?

4. May 9, 2014

### AGNuke

Two C-F bonds will repel each other, thus they will try to maximize their angle, but their repulsion with lone pair is even greater, hence they will be forced to elongate themselves in order to face minimal repulsion from each other and the lone pair.

Try to work on this.

5. May 10, 2014

### utkarshakash

If I follow through this reasoning, then CF3 will have maximum C-F bond length because it suffers more repulsion as compared to others.

6. May 10, 2014

### AGNuke

Might be. But you should check around the internet for factual data before putting your vote in my "theory".

See, I am assuming that you are preparing for college entrance exam (JEE).

7. May 10, 2014

### utkarshakash

Yes. I'm preparing for JEE and they won't ask questions where factual data is required. But what I wanted to say is that the correct answer is B) which is just the reverse of what I expected.

8. May 10, 2014

### AGNuke

Well, what can I say, I'd need to dig up some lost info on this one.

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