Overlap and Molecular Properties

The way in which orbitals overlap affects several properties of molecules, such as bond strength and molecular rotation. The mode of overlap influences bond strength because side-to-side overlap is not as extensive as end-to-end overlap. 

C—C CT bond in acetylene forms when an sp orbital of each C overlaps. Two C—H a bonds form from overlap of the other sp orbital of each C and an s orbital of an H. Two unhybridized 2p orbitals on each C are shown In stylized form (one pair is in red for clarity). B, The 2p orbitals (shown In accurate form) actually overlap side to side the a bonds are 

Therefore, we would expeet a tt bond to be weaker than a a bond, and so a double bond should be less than twice as strong as a single bond. This expectation is borne out for carbon-carbon bonds. However, many factors, such as lone-pair repulsions, bond polarities, and other electrostatic contributions, affect overlap and the relative strength of c and tt bonds between other pairs of atoms. Thus, as a rough approximation, a double bond is about twice as strong as a single bond, and a triple bond is about three times as strong. 

SAMPLE PROBLEM 11.2 Describing the Types of Bonds in Molecules 

Problem Describe the types of bonds and orbitals in acetone, (CH3)- CO. 

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The Mode of Orbital Overlap and the Types of Covalent Bonds Single and Multiple Bonds Mode of Overlap and Molecular Properties... 

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