Condensation/hydrolysis

[shinny]

Is forming/breaking apart a larger molecule a condition for condensation/hydrolysis reactions? for example, is CH3CH2OH+HBr-->CH3CH2Br+H2O considered a condensation since water is released? or is it only a substitution since a molecule hasnt actually been broken down. likewise, can ethene+water to make ethanol be considered a hydrolysis since water is reacting, or cant it because nothing has been broken down and is merely an addition?

[midas_touch]

The first reaction isn't a condensation reaction, its a substitution reaction involving a direct swap of OH- with Br-. H2O needs to come from the molecule itself in order for it to be considered a condensation reaction.

On the other hand, the second reaction is both an addition and a hydrolysis reaction, since H2O is a reactant which adds to Ethene.

[Mao]

The first reaction isn't a condensation reaction, its a substitution reaction involving a direct swap of OH- with Br-. H2O needs to come from the molecule itself in order for it to be considered a condensation reaction.

what do you mean?
the OH and H came from the reactants, what differentiates these from -OH and -H from in esterfication?
I thought condensation is just when water is a product, and hydrolysis is when water is a reactant [maybe excluding redox reactions with uses water]

[beezy4eva]

I thought condensation is just when water is a product, and hydrolysis is when water is a reactant [maybe excluding redox reactions with uses water]

Condensation is a reaction where two molecules bond to form one molecule, and  lose a small molecule. It doesn't necessarily have to be water.

I dont think the reactions you gave us could be classified as condensation or hydrolysis. Like midas said the first one would only be substitution, since its not actually a joining of two molecules. I wouldn't call the second one hydrolysis since the ethene isn't actually being split into two smaller molecules.

[Mao]

mmm it appears wikipedia agrees with you guys:

Hydrolysis:

Hydrolysis is a chemical reaction or process in which a chemical compound is broken down by reaction with water.[1][2] It is the type of reaction that is used to break down certain polymers, especially those made by step-growth polymerization.

...

In organic chemistry, hydrolysis can be considered as the reverse or opposite of condensation, a reaction in which two molecular fragments are joined for each water molecule produced. As hydrolysis may be a reversible reaction, condensation and hydrolysis can take place at the same time, with the position of equilibrium determining the amount of each product.

whereas condesation reaction is:

A condensation reaction is a chemical reaction in which two molecules or moieties (functional groups) combine to form one single molecule, together with the loss of a small molecule.
When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride, methanol, or acetic acid.

and on the note on that particular reaction of ethene + water -> ethanol:
Hydration:

In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group (OH-) and a hydrogen cation (an acidic proton) are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group.
Hydration differs from hydrolysis in that hydrolysis cleaves the non-water component in two. Hydration leaves the non-water component intact.

[shinny]

since wiki says 'other possible small molecules lost are...acetic acid', does that mean that the pathway of synthesising aspirin from salicylic acid+acetic anhydride could be classified as both an esterification AND a condensation?

in summarising the rest, so basically; a condensation which releases water is a dehydration, while a ethene+water-->ethanol is a hydration...haven't seen those two terms used often

[Mao]

since wiki says 'other possible small molecules lost are...acetic acid', does that mean that the pathway of synthesising aspirin from salicylic acid+acetic anhydride could be classified as both an esterification AND a condensation?

yes, all esterification reactions are also condensation reactions [unless there's a freak of nature example against this], as they are functional groups reacting and spitting out water.

and hydration/dehydration arent in the VCE syllabus, VCAA may refer to ethene + water -> ethanol as hydrolysis, but if asked in a question the proper answer [with respect to the syllabus] is addition reaction, and dehydration is condensation.

i'd say avoid terms that are ambiguous =]