OCR F324-June 2013 Chemistry

please help

Any predictions for the questions tomorrow?

The paper and question would help.

well I thought that always like the more hydrocarbon chain the less the solubility, but why is benzene less soluble than hepatonic acid when it has 1 less carbon atom?

is it because the benzene is unreactive because of pi electrons that are delocalised/

Hopefully a nice big NMR question since there wasn't one in jan

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Good. Just going through reaction conditions and student-foruming. How is yours?

Thin Layer:
A thin layer (funny that) of plastic / glass is coated by something like SiO2. The mobile phase- a solvent - passes over it. The dissolved substances, well... Dissolve, different amounts in the solvent, so adsorb to the thin layer at different points; thus separating the solution out.
NOTE: Solvents need to dissolve substances enough that ALL substances dissolve, but not too but that they don't adsorb at all.
Rf values: (Retention values) measure how much a substance has moved in comparison to the whole solvent, so:
Amount moved by substance / Amount substance has moved
Disadvantages: Doesn't really help identify substances as similar substances have similar Rf values.
Rf values can be compared a table of results to identify compounds.
Gas:
Substance / mixture is turned into a gas. It's mixed with a carrier gas which, uh, carries it, once injected into a tube lined with a thin layer of liquid or solid. Then either:
If lined with a liquid: Gases dissolve different amounts in a liquid, so they remain in the the tube for different amounts of time.
If lined with a solid: Gases adsorb to the surface of the solid different amounts so that they remain in the tubing for different lengths of time.
The amount of time it takes for one substance to pass through the tube and reach the end (where it is recorded and a time is taken) is called theretention time.
Different retention times indicate different molecules, so the values can be compared with already taken results that are in a table.
NOTE:
Stationary phase: The part of the chromatography that doesn't move.
-The plate lined with SiO2 in TLC
-The liquid or solid coating in the tube of GC
Mobile phase: The part of chromatography that does move.
-The solvent in TLC
-The carrier gas in GC

(It doesn't get simpler! Sorry!)

That's what I thought. That aliphatic would be more soluble compared to aromatic because of the resistance to react due to delocalised electrons and high stability. Btw, I made this question up so I don't know myself which way it goes. That's why I'm asking you lol.

If your looking at what is adjacent and it is a COOH, then do you include the H in the COOH or not? S

No because the carbon is bound to the oxygen and then that oxygen is bound to the hydrogen. The hydrogen has to be directly bonded to the carbon for it to be included in the splitting pattern

can you give me the question again, ill post it in the chem forum for a genius to answer and will let you know ASAP

sure

its a legacy the Jan 2009, the methods of analysis and detection?

question 5)a)ii)
please, dont know to upload it

Thank you so much (I know it wasn't me who asked but I needed this too LOL)
Just wondered if in GC it's liquid on solid support, is that separated by adsorption aswell? Or is there a name for it cause I saw 'Partition' somewhere but got confused...

Do you think there're any key definitions for this exam? Compared to F325 there doesn't seem to be that much at all.
I think maybe:
- Retention Time
- Amino acid
- Isoelectric Point
- Zwitterion
- Polypeptide
- Condensation/Addition polymerisation
- Stereoisomerism
- Chiral Carbon

err literally Idk anymore?

Student-foruming at present. Might take a break to do a spot of reaction condition-ing some time soon. Anything hard/tricky you've come across so far?