Length of C=O bond

[MedPR]

So TBR says the C=O bonds in caffeine (shown below) are longer than a typical non-resonance stabilized C=O bond (e.g formaldehyde, and carbon dioxide). I know that the resonance present in caffeine basically makes the double bond more like a 1.5bond (like in Benzene) so it's longer than a typical double bond. However, does the length of the bond also have anything to do with steric hindrance? There would be more hindrance in caffeine than in formaldehyde or carbon dioxide. Thus a longer double bond to create more space..?

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[chiddler]

The actual bond length between two atoms in a molecule depends on such factors as the orbital hybridization and the electronic and steric nature of the substituents.

stolen from wiki.

 

[MedPR]

The actual bond length between two atoms in a molecule depends on such factors as the orbital hybridization and the electronic and steric nature of the substituents.

stolen from wiki.

Good enough for me. Thanks!