[Big_Joe]

Can someone explain/show me the organic mechanism of but-3-en-1-ol reacting with bromine water please.

I have an idea but i'm not 100% sure.

Could someone also explain/show me the organic mechanism for the reaction of butanal with tollens reagent.

Thanks in advance.

[carboneel]

is the reaction with Br2 in h2o? or HBr in h20? 

[aldoxime_amine]

Are you aware of the reaction of an alkene with bromine (in an organic solvent, and in water)? If yes, then if you notice, in the mechanism some intermediate is formed which the hydroxy group does not like ( )...

Hint:
The hydroxy group (more specifically, the oxygen of the hydroxy group) can behave as a nucleophile, so where does that leave the situation now?

[Big_Joe]

Don't worry i sorted out the first one, i had it correct in  the first place. No idea bout the tollens though!

[Mitsunobo]

Tollens reagent ( which is ammoniacal silver oxide) oxidizes the butanal to butanoic acid. This solution can donate hydroxyl ions to the carbonyl group forming an acid (or its base since its in basic condition) thereby oxidizing the aldehyde and reducing the silver ion to a metal (mirror like). This reagent usually don't react with ketones (except for hydroxy ketones) since ketones are more resistant to oxidation than aldehydes.