VCE Chemistry Question Thread

[Sundal]

The number of possible isomers with side chains increases as the number of carbon aroms increases. The side chain can be considered as an alkane molecule that has lost a hydrogen atom. The fragment of the alkane that forms the side chain is called an alkyl group.



What does this even mean???

wunderkind52 beat me to it, but nevermind, I'll still contribute my two cents:

An isomer of a molecule is a molecule with the same molecular formula, but a different structural formula (so essentially the same type and number of elements are present, but the atoms are arranged differently). As the number of carbon atoms in the carbon-backbone of an organic molecule increases, there becomes an increased number of ways that the atoms can be arranged, while still giving the same molecular formula (however the structural formula will have changed).
In forming isomers, often part of the original molecule becomes attached elsewhere as sidechains known as alkyl groups. So for example an alkyl group derived from methane (CH4) has one less hydrogen atom than methane, thus has a formula of CH3 and is called a methyl group.

Hope that cleared some of your doubts up!

[cosine]

Thanks guys, awesome explanations!

What steps are needed to be followed when naming organic compounds? I can't seem to stick to using any specific step :/

[wunderkind52]

Thanks guys, awesome explanations!

What steps are needed to be followed when naming organic compounds? I can't seem to stick to using any specific step :/

Lots of different little rules, but
Won't go into the whole details, but for priority of functional groups see here - http://www.masterorganicchemistry.com/2011/02/14/table-of-functional-group-priorities-for-nomenclature/

General rules see here
http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry

[Sundal]

In H-NMR if you had a septet what would this signify?

Can you have 6 hydrogens attached to a Carbon?

[Splash-Tackle-Flail]

In H-NMR if you had a septet what would this signify?

Can you have 6 hydrogens attached to a Carbon?

Septet would mean there are 6 neighbouring protons iirc, but this doesn't mean there are six hydrogens attached to a carbon, which seems impossible tbh (carbon only has 4 valance electrons so a max of 4 bonds).

[cooldude123]

Does a catalyst affect the reaction mechanism?

Is the question supposed to be in terms of the reaction pathway or in terms of equilbrium and reaction rates (ie. the rate laws for a given reaction)?

[mahler004]

Does a catalyst affect the reaction mechanism?

Is the question supposed to be in terms of the reaction pathway or in terms of equilbrium and reaction rates (ie. the rate laws for a given reaction)?

A catalysed reaction will proceed via a different mechanism compared to a non-catalysed reaction (so a different pathway.) The reaction rate will be altered, but the equilibrium will be unchanged (you'll just get there faster.)

[keltingmeith]

Does a catalyst affect the reaction mechanism?

Is the question supposed to be in terms of the reaction pathway or in terms of equilbrium and reaction rates (ie. the rate laws for a given reaction)?

This is slightly beyond VCE level, though. Why do you ask?

[Sundal]

Just out of curiosity, would there be a simple explanation for why non-metals don't work in flame tests?

Also, would the state of the sample (liquid or gaseous) affect the infrared spectrum of a substance?

Thanks

[RazzMeTazz]

Can someone please help with this question (attached below) !

I wasn't quite sure what the trough at wave number 1720 would be.
I thought it would be C=O, but since I had the trough at 3000 as being due to OH I wasn't sure, since the molecule only has one oxygen! Thanks

[Sundal]

Septet would mean there are 6 neighbouring protons iirc, but this doesn't mean there are six hydrogens attached to a carbon, which seems impossible tbh (carbon only has 4 valance electrons so a max of 4 bonds).

Oh okay so for instance it could mean like 3 H's on one of the adjacent carbons and 3 H on the other adjacent carbon ?

[wunderkind52]

Can someone please help with this question (attached below) !

I wasn't quite sure what the trough at wave number 1720 would be.
I thought it would be C=O, but since I had the trough at 3000 as being due to OH I wasn't sure, since the molecule only has one oxygen! Thanks

I think the 1720 is a C=O. And the trough at 3000 is C-H. Notice that it's a sharp peak, and OH is normally has broad peaks.
I'm guessing it's propanone.
Also, something I learnt from Thushan is double bond equivalents. No matter how you arrange your molecule, you will always have a double bond. More information here Double Bond Equivalent Formula

However, in short, think of your unsaturated hyrocarbon - C3H8. You've replaced 2Hydrogen atoms with one oxygen atom, which basically means that you now have a double bond somewhere.

[paper-back]

Are amide and peptide functional groups the same thing?

[keltingmeith]

Are amide and peptide functional groups the same thing?

Yes.

[RazzMeTazz]

Are the terms 'retention factor' and 'retardation factor' in chromatography, synonymous?