C=O bond length comparison among cyclohex‐2‐en‐1‐one and cyclohex‐3‐en‐1‐one

[![1: cyclohex‐2‐en‐1‐one; 2: cyclohex‐3‐en‐1‐one](https://i.stack.imgur.com/RNxI3.png)](https://i.stack.imgur.com/RNxI3.png)


I can see that in the first case a resonance would occur, and in the second case, there would be no resonance effect. I have read the fact that resonance reduces bond length due to partial double bond character. 


According to that, shouldn't the $\ce{C=O}$ bond length in **1** be lesser than that in **2**? The answer in my book is that the $\ce{C=O}$ bond in **1** is longer (reason is simply given as: "Resonance"). Could someone help me understand what's going on here?




The case **1** has partial double bond character (due to resonance) while case **2** has total double bond character of the C-O bond. So, relative to case **2**, the C-O bond length in case **1** is longer.


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