what is wrong with my explanation?

[liv]

here is what i wrote for my explanation of esterification on my first sac, and apparently i don't understand functional groups enough:

Esterification is a process by which two reactants, a carboxylic acid and an alcohol, in the presence of another acid (such as H2SO4) form an ester and water . An ester is a molecule that contains the ester COO functional group . This production of water also classifies this as a condensation reaction, and this can also be reversed. The hydrogen from the hydroxyl group of the alcohol bonds with hydroxide from the carboxyl group of the acid, and this forms water.  If the alcohol, however, is an anhydride, then not water but the acid of the alcohol is produced. The loss of the hydrogen creates a negative charge on the alcohol, and the loss of the hydroxide from the acid creates positive charge, so these are covalently bonded together. This makes an ester and water, and there is sometimes some acid left over

what am i missing? the sac is obviously over but what did i do wrong? the teacher won't tell me exactly.

[Potter]

here is what i wrote for my explanation of esterification on my first sac, and apparently i don't understand functional groups enough:

Esterification is a process by which two reactants, a carboxylic acid and an alcohol[Esters aren't only formed by carboxylic acids and alcohols], in the presence of another acid (such as H2SO4)[explain that this is a catalyst in the reaction, you make it sound like it's involved with the reaction.] form an ester and water . An ester is a molecule that contains the ester COO functional group [This part doesn't really make sense to me.]. This production of water also classifies this as a condensation reaction, and this can also be reversed How can the reaction be reversed? Should explain. Otherwise don't mention it at all.. The hydrogen from the hydroxyl group of the alcohol bonds with hydroxide[Don't use interchangeably.]  from the carboxyl group of the acid, and this forms water.  If the alcohol, however, is an anhydride, then not water but the acid of the alcohol is produced.[Should give en example so you can reinforce what you're saying. Shows greater understanding/depth.] The loss of the hydrogen creates a negative charge on the alcohol, and the loss of the hydroxide from the acid creates positive charge, so these are covalently bonded together. [If you have a cation and an anion, isn't that ionic bonding?] This makes an ester and water, and there is sometimes some acid left over [When is there sometimes some acid left over? The acid is used as a desiccate. This puts forward the reaction, producing a higher yield.]


Overall, not too bad. You have to watch your language. Using the right terminology in chemistry is vital.

In an explanation you should incorporate different examples of reactions to show that you have a strong understanding of what you're on about.

An ester is a molecule that contains the ester COO functional group

I wouldn't use ester when you're giving a definition. Something like -

An ester is a functional group which takes the empirical formula of COO. One of the Oxygens creates a double bond with the carbon. The other oxygen creates a single bond.

[Mao]

A few notes:

1. Esterification can occur when sulfuric acid is not present. The reaction occurs slowly. Sulfuric acid in this case acts as a catalyst [it acts as a dehydrating agent, but also supplies H+ necessary for the reaction]. The process of esterification does not necessarily imply a catalyst is required.

2. Esterification is not confined to the reaction between a carboxylic acid and alcohol. It is correct in saying that an ester is a molecule that contains the COO group, but it should be made clear that an ester contains the functional group COOR.

3. Synthesizing an ester from other reactants:
acid anhydride [not alcohol anhydride] + alcohol
acyl halide [RC(=O)X] + alcohol
carboxylate salt + alcohol

4. The reaction is a condensation reaction. However, the origin of the water molecule (where the OH and H comes from) is beyond the VCE syllabus. You should avoid talking about the reaction mechanism, simply stating 'a water molecule is removed' is enough. You should especially avoid talking about where the electrons in bonds go to, you're treading very dangerous waters there stating one is anionic and one is cationic. See http://en.wikipedia.org/wiki/Fischer_esterification if you want a closer look at the reaction mechanism.

5. Somestimes some acid is left over, what times? which acid? [The catalyst or the carboxyl?]

You have given a good explanation, but instead of focusing on VCE level material, you have chose to focus on the reaction mechanism, which strictly speaking is not answering the question. Your explanation of the reaction mechanism is also technically incorrect, e.g. the OH in COOH is still called a hydroxyl group [not a hydroxide, which is the OH- ion], and by discussing these advanced materials in a slightly incorrect way, you have dug a hole for yourself.

My take on it is your teacher would have noticed you 'alcohol anhydride', and counted the rest of the paragraph as 'babble', hence marking it down.

[liv]

wow.
thank you.

i obviously don't know enough chemistry.

the only thing is he did want us to talk about the reaction mechanism. in great detail.

[hhland]

Wow is this on organic chemistry? Do some schools start organic chemistry before the volumetric analysis stuff etc...?

[liv]

i don't know why but we have....
 but only in this sac. we haven't actually studied an organic chemistry.