Can I assume or imply that the C=O in an ester linkage to be taken as a carbonyl group as well?
That is to say, can C=O in ester undergo reactions similar to ketones?
If I have CH3COOCH2CH3, can I use the tri-iodomethane test to distinguish it from, say CH3OOCCH2CH3?
>>> Can I assume or imply that the C=O in an ester linkage to be taken as a carbonyl group as well? <<<
Yes, of course it's a carbonyl group (defined simply as C=O); but that does not necessarily mean a carbonyl group in an ester will always behave identical to carbonyl groups in aldehydes and ketones - it certainly doesn't.
>>> That is to say, can C=O in ester undergo reactions similar to ketones? <<<
Only to a limited extent, in some reactions only.
>>> If I have CH3COOCH2CH3, can I use the tri-iodomethane test to distinguish it from, say CH3OOCCH2CH3? <<<
No, the iodoform test will not work for methyl esters, methyl carboxylic acids, methyl amides, etc. It only works (ie. gives positive result) with methyl aldehydes, methyl ketones, and methyl secondary alcohols (that can be oxidized to methyl ketones).
To distinguish both compounds you stated above, carry out hydrolysis, then oxidation. CO2 gas will only be produced for the (reaction pathway products from the) parent compound CH3COOCH2CH3, but not for CH3OCOCH2CH3.