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.