OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD

It's true. Vegetable oils are unsaturated and are liquid, margarine has less double bonds and is solid. I don't know why it's true though

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I believe the main factor is whether they are cis or trans, as cis molecules don't 'stack' well, where as trans 'stack' pretty much linearly so the molecules are closer together giving rise to increased IMF's. So the IMF's are weaker in cis molecules giving them a lower melting point.

Less double bonds generally means a straighter molecules so increased IMF's.

(edited 7 years ago)

Reply 621

Professor L

14

Original post by tcameron

so if the peak is at 3.5ppm but they say it's meant to be at 2.5ppm would we identify it as if it were at 2.5 ppm and not at 3.5ppm as out assignment of that peak or would we still do it like it was at 3.5ppm?

The former, wherever they say it's meant to be, that's what you assign it as :smile:

Reply 622

nuttynatty999

Does anyone have any predictions for the papers?

Reply 623

L'Evil Wolf

6

Someone explain this, my friend did but I didn't get it completely.

If benzene was reacted with CH3CHClCH3 in the presence of AlCl3, identify the organic product that would be formed!

Thanks

Reply 624

EricPiphany

17

Original post by L'Evil Wolf

Someone explain this, my friend did but I didn't get it completely.

If benzene was reacted with CH3CHClCH3 in the presence of AlCl3, identify the organic product that would be formed!

Thanks

I believe you can think of the AlCl3 reacting with the 2-chloropropane to remove the chlorine atom from 2-chloropropane, forming AlCl4- and (CH3)2CH+, which is an electrophile and reacts with benzene in the regular electrophilic substitution mechanism.

In reality it might be slightly more complex.

Reply 625

L'Evil Wolf

6

Original post by EricPiphany

I believe you can think of the AlCl3 reacting with the 2-chloropropane to remove the chlorine atom from 2-chloropropane, forming AlCl4- and (CH3)2CH+, which is an electrophile and reacts with benzene in the regular electrophilic substitution mechanism.

In reality it might be slightly more complex.

Thank you sir.

Reply 626

L'Evil Wolf

6

Original post by EricPiphany

I believe you can think of the AlCl3 reacting with the 2-chloropropane to remove the chlorine atom from 2-chloropropane, forming AlCl4- and (CH3)2CH+, which is an electrophile and reacts with benzene in the regular electrophilic substitution mechanism.

In reality it might be slightly more complex.

do you have any good notes on figuring out what the electrophile is :smile:

Thankn you

Reply 627

EricPiphany

17

Original post by L'Evil Wolf

do you have any good notes on figuring out what the electrophile is :smile:

Thankn you

No, I don't. In general an electrophile is an electron deficient species, that can accept a lone pair of electrons forming a covalent bond.
Attracted to high electron density.

Reply 628

L'Evil Wolf

6

Original post by EricPiphany

No, I don't. In general an electrophile is an electron deficient species, that can accept a lone pair of electrons forming a covalent bond.
Attracted to high electron density.

Oh okay thanks

Reply 629

L'Evil Wolf

6

For the percentage yield is it in terms of moles or mass that you divide by?

Reply 630

tcameron

19

Original post by L'Evil Wolf

For the percentage yield is it in terms of moles or mass that you divide by?

doesn't really matter as works both ways
But the proper way is using the mass

Reply 631

Serine Soul

18

Original post by L'Evil Wolf

For the percentage yield is it in terms of moles or mass that you divide by?

It's the same but I've always used moles.

Reply 632

Serine Soul

18

Besides some reactions, mass spec and IR, how much of AS are we expected to remember? I'm going to read over my AS notes today

Reply 633

AqsaMx

5

Original post by Serine Soul

Besides some reactions, mass spec and IR, how much of AS are we expected to remember? I'm going to read over my AS notes today

I feel like chemistry is only synoptic in the sense of empirical formula, some definitions, all the reaction mechanisms and what you've said tbh. But I'm going over everything too briefly..