1. A Review of General Chemistry

(••••) The C―H σ bond length in ethane is 1.09 Å. The C―H σ bond in ethene is 1.07 Å. Explain. [See Assessment 2.70.]

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ethane ethene

(••••) In propene, the indicated C―C bond length is 1.51 Å. In the allyl cation, the indicated C―C bond length is 1.41 Å. Explain. [See Assessment 2.68.]

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propene allyl cation

(••••) The C―N bond in the following amide is much stronger than the C―N bond in the amine. Explain. [See Assessment 2.68.]

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amide amine

Rank C―H σ the following bonds in terms of their bond length. Explain your ranking ( 1= longest ; 3 = shortest).

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(••) For the following partial structures, the bond is shown. Add the indicated number of bonds, being sure to specify the orientation (that is, x, y, or z axis) of the p orbitals used.

(a) <IMAGE> ( 2 π bond)

The molecular orbital picture of H₂ can be represented by the following diagram. Label σ and σ* on the diagram—that is, which is (a) and which is (b)? Which is lower in energy? Why?

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(•••) Given the Lewis structures, indicate the direction of the dipole moment, if there is one. [See Assessment 2.63.]

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a. How many s bond orbitals are available for overlap with the vacant p orbital in

1. the isobutyl cation? 2. the n-butyl cation? 3. the sec-butyl cation?