# Distance between atoms in a bond

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1. Aug 28, 2015

### zachem62

Here's the question:

The structure of 1,3-butadiene is usually written as H2C=CH–CH=CH2. The average bond lengths given in Table 9.2 in my textbook are: C–C of 154 pm and C=C of 133 pm. Explain the fact that the observed value of the distance between the two central carbon atoms in 1,3-butadiene is 146 pm.

Are the 2 central carbon atoms the 2 carbons that have a double bond between each other? If so, the distance of C=C is equal to 133pm so why would the distance between the 2 central carbon atoms that are double bonded be different? How else would I answer this question? THanks.

2. Aug 28, 2015

### Bystander

Number the carbon atoms from 1-4, beginning to end of chain; "central" means "middle" of chain.

3. Aug 28, 2015

### zachem62

so the central carbon atoms would be the ones in CH-CH. But I'm still not getting why the distance between these would be different than the given C-C distance.

4. Aug 28, 2015

### Bystander

You've seen/read a discussion of sp2, and/or sp3 hybrid orbitals?

5. Aug 28, 2015

### zachem62

yeah i have, maybe its super obvious and i'm not seeing the connection?

6. Aug 28, 2015

### Bystander

What are the hybrids for 1, 2, 3, and 4?

7. Aug 29, 2015