VCE Chemistry Question Thread

[2NE1]

Both the amide group and peptide bonds is the same but the term amide bond is used for simple molecules and the term peptide bond is used for polymers where a large chain of polymer is formed due to amide bonds as in poly peptide and also in proteins. But VCAA usually accepts both when they say "name the bond" for peptide bond/amine group

There is a difference between PEPTIDE LINK/BOND AND AMIDE GROUP , yeah?

VCAA 2004 Question 8 Exam 2 asks us to
Circle the peptide link

And they showed it as CONH group

WHEREAS,

I thought the peptide link is the covalent bond between C atom and N atom  ie C-N
And CONH is the amide group including a peptide link


What are your thoughts?

[Yacoubb]

As aforementioned, an amide linkage is the same as a peptide bond. I refer to amide linkages in simple molecules, and peptide covalent bonds in proteins.

[Reus]

There is a difference between PEPTIDE LINK/BOND AND AMIDE GROUP , yeah?

VCAA 2004 Question 8 Exam 2 asks us to
Circle the peptide link

And they showed it as CONH group

WHEREAS,

I thought the peptide link is the covalent bond between C atom and N atom  ie C-N
And CONH is the amide group including a peptide link


What are your thoughts?

Yes they're the same.

[Robert123]

Both the amide group and peptide bonds is the same but the term amide bond is used for simple molecules and the term peptide bond is used for polymers where a large chain of polymer is formed due to amide bonds as in poly peptide and also in proteins. But VCAA usually accepts both when they say "name the bond" for peptide bond/amine group

I don't think your definition for peptide bond is 100% correct.
A peptide bond is the bond between two amino acids but is not called that for all long polymers.
If you have a di-carboxy (not sure if that's the right name for 2 COOH on the same monomer) and a di-amino (two amino groups on the same monomer), then when they undergo polymerisation to form a long chain, the linkage is just called amide (I believe)
Interestingly, this is how nylon form of you want to go look at more info on this
So peptide is the name for them in protein where amide is the name for them in any other scenario (I beliece)

[kawfee]

Thank you all

Also, amine is the organic compound that contains amino group ? We'd lose a mark if we switch the names, right?
For instance if we label a functional group as an amine functional group.


And,

alpha amino acid definition = amino acid with the carboxy f.g, amino f.g, H atom and Z side group/constituent bonded to the same Carbon atom.

is the H atom and Z side group thing fine or necessary?

[sparksfly]

Is there a difference between carboxy and carboxyl groups in terms of naming COOH? Are they both generally accepted?


When you go from a solid to a gas- is this exothermic or endothermic, and why? I cant seem to get my head around this concept.


Thank you everyone

[Robert123]

When you go from a solid to a gas- is this exothermic or endothermic, and why? I cant seem to get my head around this concept.


Thank you everyone

I presume it is endothermic because you are breaking bonds and going into a higher energy state.
Also, applying le chatelier's principle. Hotter temperature favour endothermic reaction, therefore, since conversion of solid to gas occur at hotter temperature, it is an endothermic (I don't think this justification using le chatelier's principle is very scientific but it does the job  )

[2NE1]

Is there a difference between carboxy and carboxyl groups in terms of naming COOH? Are they both generally accepted?

yes VCAA accepts both because they have them in their answers

[Yacoubb]

Thank you all

Also, amine is the organic compound that contains amino group ? We'd lose a mark if we switch the names, right?
For instance if we label a functional group as an amine functional group.


And,

alpha amino acid definition = amino acid with the carboxy f.g, amino f.g, H atom and Z side group/constituent bonded to the same Carbon atom.

is the H atom and Z side group thing fine or necessary?

I always call the -NH2 group in an amino acid the amine group.

An alpha amino acid is an amino acid made up of a central carbon atom, to which is attached a carboxyl group, an amine group, a hydrogen atom and a Z-side group. I accompany it with a diagram if I've been given enough room OR it's worth more than 1 or two marks.

[kawfee]

@ Yacoubb

Hmm yeah, I think I named that group ie -NH2  as amine , primary amine, secondary etc too...but sometimes I change to the other :S

But do you think for those compounds like 2 butanamine (that's a legit compound right? ) you call it an amine...but the constituent/f.g amino group? and not amine group?

[2NE1]

For this question VCAA says the answer is H or H atom, why isn't it H radical?

[Yacoubb]

@ Yacoubb

Hmm yeah, I think I named that group ie -NH2  as amine , primary amine, secondary etc too...but sometimes I change to the other :S

But do you think for those compounds like 2 butanamine (that's a legit compound right? ) you call it an amine...but the constituent/f.g amino group? and not amine group?

2-butanamine is actually the IUPAC name. If I remember correctly, it used to be called (the old IUPAC name) 2-amino butane, which is now wrong. I don't think there is necessarily a right answer in terms of using amino or amine (I use amine, not sure if amino can be used), but I'd stick with amine.

[psyxwar]

2-butanamine is actually the IUPAC name. If I remember correctly, it used to be called (the old IUPAC name) 2-amino butane, which is now wrong. I don't think there is necessarily a right answer in terms of using amino or amine (I use amine, not sure if amino can be used), but I'd stick with amine.

Actually the IUPAC name is butan-2-amine

[Yacoubb]

For this question VCAA says the answer is H or H atom, why isn't it H radical?

Because when the hydrogen atom is lost, CH3CHOH+ is the radical produced.

Actually the IUPAC name is butan-2-amine

Wait, isn't 2-butanamine = butan-2-amine?? :S is my whole life a lie, lol?

[lzxnl]

Wait, isn't 2-butanamine = butan-2-amine?? :S is my whole life a lie, lol?

They refer to the same molecule, although the second name more appropriately places the '2' closer to the functional group.

For this question VCAA says the answer is H or H atom, why isn't it H radical?

Actually a hydrogen atom IS a radical...you should be correct there

Because when the hydrogen atom is lost, CH3CHOH+ is the radical produced.

CH3CHOH+ isn't a radical; just saying. You have an even number of electrons. It's basically CH3CH2OH minus a H-