Eclipsed vs. Staggered. Trigonal Carbons

Molecules prefer conformations that stagger bonds on neighboring tetrahedral carbons (see Chapter 5, Problem 1). Does the same apply to trigonal carbons  

Organic chemists usually think of a double bond as the combination of a a bond and a 7i bond. An alternative is to consider a double bond as made up of two equivalent bent bonds (these bonds point above and below the intemuclear axis). 

Apply the bent-bond model to the preferred conformations of acetaldehyde and propene. Do bent-bonds maintain or remove eclipsing interactions in the equilibrium structures of the two molecules Formulate a simple rule based on the bent-bond model for predicting conformational preferences in systems containing trigonal atoms. 

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