Question

What is the order in terms of decreasing acidity?

Answer 1

Well, the more carbonyl groups proximate to the carbon which bears the acidic protons....

Explanation:

...the more that carbanion should be stabilized upon abstraction of that proton. Given this rule of thumb, the order or acidity...with the LEAST acidic molecule to the LEFT should be:

.......... `stackrel(IV, II, I, III)rarr` ..........
`"order of increasing acidity"`

The carbanionic charge of molecule `III`is potentially distributed over SEVEN centres, and thus should be the most acidic.

Note that as a chemist, as a physical scientist, you should put forth some data in support of your argument, and quote the `pK_a` values of each species. For cyclohexane, the value will be around `50`...I think there is such a table of `pK_a` of carbon acids in March...