Okay, we've established that intramolecular hydrogen bonding can exist in molecules, and doesn't always serve the purpose of closing the bond angle at least relative to other stereoisomers of the same compound.
Consider nitrous acid and its cis and trans configuration; hydrogen bonding is only a possibility in the cis configuration, yet the cis conformation has (rather unexpectedly) a larger bond angle than in the trans conformation. The same goes for nitric acid.
Why does nitrous acid exhibit (unexpectedly) different bond angles?
So, are there actually any examples of molecules in which internal hydrogen bonding serves the purpose of closing up the bond angle relative to other conformations of the same molecule?
