VCE Chemistry Question Thread

[warya]

How can glycerol be oxidised by MnO4-/H+? I thought only primary alkanols could be oxidised, can there be more than one OH group that forms carboxylic acid?

[lzxnl]

How can glycerol be oxidised by MnO4-/H+? I thought only primary alkanols could be oxidised, can there be more than one OH group that forms carboxylic acid?

Glycerol has two primary alcohol groups and one secondary alcohol group. Both can be oxidised by aqueous acidic permanganate. Secondary alcohols become what are called ketones.

[warya]

In my notes it says only primary alcohols can be oxidised, if we are comparing how fast glycerol oxidises compared to propan-1-Ol and propan-1,2-diol, should I ignore what my teacher has said and just say it's a ketone

[lzxnl]

In my notes it says only primary alcohols can be oxidised, if we are comparing how fast glycerol oxidises compared to propan-1-Ol and propan-1,2-diol, should I ignore what my teacher has said and just say it's a ketone

Well, your notes are probably incomplete then. You can oxidise secondary but not tertiary alcohols.
As for rate of oxidation, it has three sites of reaction compared to the one and two in the other two molecules...so yeah

[lisax3]

Has anyone done the DNA -proteins data analysis sac? I'm not really sure what to expect. What data does it involve analysing? And what questions do they ask?

[Kel9901]

In my notes it says only primary alcohols can be oxidised, if we are comparing how fast glycerol oxidises compared to propan-1-Ol and propan-1,2-diol, should I ignore what my teacher has said and just say it's a ketone

oxidation of secondary alcohols is not on the course

[I am a unicorn]

Hi
Does the (n+1) peak splitting rule apply for benzene rings??
Thanks

[keltingmeith]

Hi
Does the (n+1) peak splitting rule apply for benzene rings??
Thanks

No - but, you will never be asked about benzene rings in VCE. The study design very specifically mentions that students do not work with cyclic molecules, so you won't have to worry about that.

[Rishi97]

No - but, you will never be asked about benzene rings in VCE. The study design very specifically mentions that students do not work with cyclic molecules, so you won't have to worry about that.

...and then you get to uni... -_-

[I am a unicorn]

Hi

In my teachers notes, it says 'amino acids can form ion-dipole interactions with water molecules'.
Is this true? or my teacher notes wrong?? because i dont get how this would happen as amino acids are not ionic compounds...

Thanks! 

[mahler004]

Hi

In my teachers notes, it says 'amino acids can form ion-dipole interactions with water molecules'.
Is this true? or my teacher notes wrong?? because i dont get how this would happen as amino acids are not ionic compounds...

Thanks! 

Some residues are changed - e.g. the guanidium group in arginine or the amino group in lysine. These can interact with water molecules (or other amino acids,) in the manner your teacher suggested.

Free amino acids are charged - depending on the pH they can adopt a multiple of charge states.

[I am a unicorn]

Can carboxylic acids undergo combustion reactions??
Thanks

[mahler004]

Can carboxylic acids undergo combustion reactions??
Thanks

Yep

[biy]

Whats the difference between amino acids and zwitterions?
How can we go from an amino acid to a zwitteroin?
How does pH affect an amino acid zwitterion? (with examples, please)
Regarding the bonds of proteins and their structures, how can you describe the secondary structure, and what bonds are responsible for the alpha helices and b pleated sheets to form?
What types of bonds can form between enzymes and their specific substrate?

many thanks <3

[keltingmeith]

Whats the difference between amino acids and zwitterions?

All amino acids (in VCE, at least. inb4 someone who actually knows biochem knocks me back) are zwitterions, not all zwitterions are amino acids. A zwitterion is a type of ion that shows a positive and negative charge at the same time, an amino acid is just a type of zwitterion (hence the name "amino acid" being kinda stupid)

How can we go from an amino acid to a zwitteroin?

By putting that amino acid into solution.

How does pH affect an amino acid zwitterion? (with examples, please)

Consider the following examples:

Acidic pH:
The solution will be absolutely drenched with protons - they're absolutely everywhere. So, your amino acid's carboxyl group is very likely to get protonated.

Neutral pH:
There's no excess of protons or hydroxides, so our amino acid will simply exist in zwitterion form.

Basic pH:
The solution will be absolutely drenched with hydroxides (as opposed to protons). So, these hydroxides will try to grab onto a proton whenever it can - so, it will take the excess proton on the amine group of the amino acid.

Regarding the bonds of proteins and their structures, how can you describe the secondary structure, and what bonds are responsible for the alpha helices and b pleated sheets to form?

Usually, through covalent bonds, di-sulfide bridges and other intermolecular forces.

What types of bonds can form between enzymes and their specific substrate?

Any bond ever - but, normally they're just hydrogen bonds.