VCE Chemistry Question Thread

[Jackxm97]

Does anyone know what the functional groups are in ethanoic acid, salicyclic acid, acetic anhydride and aspirin?
Thanks 

[keltingmeith]

Does anyone know what the functional groups are in ethanoic acid, salicyclic acid, acetic anhydride and aspirin?
Thanks 

Ethanoic acid: Carboxylic acid

Salicylic acid: Alcohol, carboxylic acid, aromatic ring

Acetic anhydride: Ester, ketone

Aspirin: Ester, carboxylic acid, aromatic ring

You should be able to identify most of these yourself - if you can't, revise functional groups.

[Jackxm97]

Cheers

[Sundal]

Can someone please help me out!

 I don't get why alkanoic acids are generally more soluble than alkanols. I know it's something to do with the fact that the COOH group of the alkanoic acid contains the double covalent bond between C and O, but I'm a little unsure.

Additionally, in my chemistry textbook it is written: "Alkanoic acids are stronger acids than their corresponding alcohols because the —OH group is more polarised in the —COOH group by the presence of the highly electronegative O atom of C=O. This =O atom attracts the electrons towards it and away from the —OH group. Therefore, the H is more weakly bonded to O and is more easily donated."

Since the electrons are attracted towards the C=O and away from the -OH group, does this mean electrostatic forces of attraction in the -OH decrease, resulting in H being more weakly bonded to O and thus more easily able to be donated?

Cheers

[Macka598]

Can someone please help me out!

 I don't get why alkanoic acids are generally more soluble than alkanols. I know it's something to do with the fact that the COOH group of the alkanoic acid contains the double covalent bond between C and O, but I'm a little unsure.

Additionally, in my chemistry textbook it is written: "Alkanoic acids are stronger acids than their corresponding alcohols because the —OH group is more polarised in the —COOH group by the presence of the highly electronegative O atom of C=O. This =O atom attracts the electrons towards it and away from the —OH group. Therefore, the H is more weakly bonded to O and is more easily donated."

Since the electrons are attracted towards the C=O and away from the -OH group, does this mean electrostatic forces of attraction in the -OH decrease, resulting in H being more weakly bonded to O and thus more easily able to be donated?

Cheers

as far as solubility goes i think the reason why COOH groups are more soluble than the corresponding OH groups is because of COOH ability to form Hydrogen bonding with water moreso than OH groups as there is two Oxygens in the COOH and therefor more h-bonds leading to increaced solubility. im not sure about the acidity though.

[Sundal]

Since the functional groups of ethers, amides, aldehyde and ketones aren't on the study design, does that mean we don't need to know about them?
Or is it best to still have an idea about them?

Also, can someone explain the "first point of difference rule" used in organic compound nomenclature?

Cheeers 

[jessss0407]

Hi everyone,

I'm struggling a bit with the IUPAC naming system - does anyone know an easy way to remember the rules (mainly the whole precedence and numbering bit)

Also, do double and triple bones have priority over halogens/functional groups? Thanks

[sunshine98]

Also, do double and triple bones have priority over halogens/functional groups? Thanks

Double and triple bonds take precedence over halogens and alkyl groups , but do not take precedence over the principle functional groups (carboxyl, hydroxyl and amine) 

[lzxnl]

Double and triple bonds take precedence over halogens and alkyl groups , but do not take precedence over the principle functional groups (carboxyl, hydroxyl and amine)

Double takes precedence over triple. Just a weird rule to add.

[jessss0407]

Hi,

I was wondering, if strucutral isomers have the same molecular formula, why would they have different chemical properties?

Thanks

[niccigriffin35]

help!!! I've got a SAC tomorrow for the spectroscopy SAC and I wasn't there for the experiment so I'm really freaking out

[keltingmeith]

Hi,

I was wondering, if strucutral isomers have the same molecular formula, why would they have different chemical properties?

Thanks

Because they're arranged differently. Consider ethanoic acid (CH3COOH) (C2H4O2) and methyl-methanoate (CHOOCH3) (C2H4O2). As you can see, they are structural isomers of each other - but, they have completely different functional groups, just because of the way they're arranged.

help!!! I've got a SAC tomorrow for the spectroscopy SAC and I wasn't there for the experiment so I'm really freaking out

What do you need help with?

[RazzMeTazz]

Would this be a correct explanation for why different metals produce different colours to each other in a flame test?

Each metal atom has a differing number of protons and as such the electrostatic attraction between the electrons and  varies. Consequently, the distance of electron shells from the nucleus and thus their energy levels also vary. Therefore valence electrons belonging to these metals emit unique wavelengths of light when returning from their excited state to their ground state.

Thanks in advance!

[keltingmeith]

Would this be a correct explanation for why different metals produce different colours to each other in a flame test?

Each metal atom has a differing number of protons and as such the electrostatic attraction between the electrons and  varies. Consequently, the distance of electron shells from the nucleus and thus their energy levels also vary. Therefore valence electrons belonging to these metals emit unique wavelengths of light when returning from their excited state to their ground state.

Thanks in advance!

No - at your level, you do not know enough to comment on why different metals produce different colors. You need MO theory to explain this.

[RazzMeTazz]

No - at your level, you do not know enough to comment on why different metals produce different colors. You need MO theory to explain this.

Oh okay thanks! I was just wondering since one of my textbook questions was: Barium and calcium are both Group II elements. Account for the observation that samples of barium and calcium compounds produce different colours when they are held in a flame.

And the answer was: As a consequence of the presence of different numbers of protons in the nuclei of barium and calcium atoms, the energies of electrons in the shells of the two atoms are not the same. Different amounts of energy are released when an electron moves from a higher energy level to a lower one in a barium atom compared with when the same process occurs in a calcium atom. These different energies are seen as light of different colours.

Does this correspond with MO theory, or..?