The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

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

Scroll to see replies

Original post by KB_97
Would part e)i) be nucleophilic addition mechanism? And is part ii) basically that: A molecule with a chiral centre is made. It has two optical isomers, each of which rotate plane polarised light in opposing directions. Therefore the racemix mixture would have no effect on plane polarised light. ?? How do you get three marks out of that?


Yeah but you also need to talk about the fact that the nucleophile can attack from above or below the plane, as the shape around C=O is trigonal planar (F321 synoptic link) https://gyazo.com/c8fc67089ae33f79b945cb1f0a2aeb9f

My teacher went through this, not sure if we need to know about the attacking from above/below but just in case :smile:
Will they mark an annotated mass spec?????
Original post by Serine Soul
That one with fluoride ion and benzene?


Original post by safhassan
Question 2 b


Was that the horrible one with the two Br? crazy question
Original post by itsConnor_
Was that the horrible one with the two Br? crazy question


that is 2c when they give a reaction that is not in the spec, and you never heard about before ( at least for me)
Original post by suibster
So if a hydrogen is connected to a C that is also connected to 2 other carbons with different functional groups on each side, the splitting would be a multiplet, what if the neighbouring groups are not carbon? would the splitting be a multiplet still?


In H-NMR spectroscopy, the splitting refers to the number H-Atoms on adjacent Molecules (No. Peaks = No. Adjacent H-Atoms + 1). For example:

H3C-CH2-CH3 } The central carbon atom (CH2) would have a split pattern with 7 Peaks because the groups next to it have 6 H-Atoms attached to them.
H3C-CH2-NH2 } In this case, the central Carbon atom would have a split pattern with 6 peaks because the groups directly next to it are attached to a total of 5 H-Atoms. This applies even if the atom is not a Carbon.

Hope this helps, happy to answer any further questions, but may be a bit later in replying.
Original post by lai812matthew
in nucleophilic attack, there are two possible position that the OH/ H group is placed.
the chance of it being placed one or the other way round is completely random i.e. 50/50. therefore the ratio of each optical isomer form is 1:1, i.e. a racemic mixture, therefore it will not be optically active, no effect when there is plane polarised light


Where did the h/oh come from. I thought you had to add CN-
Original post by tcameron
NaOH equilibrium reaction? Is this the making soaps stuff


you could make soap from the similar mechanism but with NaOH instead of CH3OH (biodiesel)
Reply 1167
Avatar for Cal 1
Cal 1
2
For question 2)e)ii) of OCR f324 (Link: http://www.ocr.org.uk/Images/175441-question-paper-unit-f324-01-rings-polymers-and-analysis.pdf ) what kind of reaction is 'reaction 2'? and why is CuI used? can't seem to find diazonium ions reacting other than during coupling! Thanks
Original post by KB_97
Where did the h/oh come from. I thought you had to add CN-


sorry it's CN- not OH-
Original post by lai812matthew
that is 2c when they give a reaction that is not in the spec, and you never heard about before ( at least for me)


do you understand the crazy one? my teacher tried to explain it to me and i think i get it now

Also that nucleophilic sub looks very different to the AS mech :redface:
Original post by MrJackAT
In H-NMR spectroscopy, the splitting refers to the number H-Atoms on adjacent Molecules (No. Peaks = No. Adjacent H-Atoms + 1). For example:

H3C-CH2-CH3 } The central carbon atom (CH2) would have a split pattern with 7 Peaks because the groups next to it have 6 H-Atoms attached to them.
H3C-CH2-NH2 } In this case, the central Carbon atom would have a split pattern with 6 peaks because the groups directly next to it are attached to a total of 5 H-Atoms. This applies even if the atom is not a Carbon.

Hope this helps, happy to answer any further questions, but may be a bit later in replying.


I don't know man but i would said the first one is a quartet of quartets, and the second one is a quartet
(edited 7 years ago)
Original post by itsConnor_
do you understand the crazy one? my teacher tried to explain it to me and i think i get it now

Also that nucleophilic sub looks very different to the AS mech :redface:


If this is in F322 (it can be), a lot of people would get this wrong also. more of a test of whether you know how the curly arrows work other then testing the mech really.
When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light

does this mean that synthetically made drugs are racemic mixtures so would not rotate plane polarised light? So it only occurs with natural optical isomers
Original post by itsConnor_
Yeah but you also need to talk about the fact that the nucleophile can attack from above or below the plane, as the shape around C=O is trigonal planar (F321 synoptic link) https://gyazo.com/c8fc67089ae33f79b945cb1f0a2aeb9f

My teacher went through this, not sure if we need to know about the attacking from above/below but just in case :smile:


Oh okay. the thing about attacking from top or bottom isn't on our spec though is it? I think we just need to know about racemix mixtures and plane polarised light etc.

Also can someone show me what the mechanism for the question e)i) looks like please.
Original post by Vannzzoo
Will they mark an annotated mass spec?????


yeah
Original post by lai812matthew
I don't know man but i would said the first one is a quartet of quartets, and the second one is a quartet of triplets (or the other way round i forgot).


are we meant to include N-H as contributing to the splitting??
Original post by tcameron
are we meant to include N-H as contributing to the splitting??


http://www.chem.ucla.edu/~harding/IGOC/T/triplet_of_doublets.html, yeah we shouldn't be so that would be a quartet
Original post by lai812matthew
http://www.chem.ucla.edu/~harding/IGOC/T/triplet_of_doublets.html, yeah we shouldn't be so that would be a quartet


yeah I didn't think we included them either because they always are classed as singlets in the nmr spectra so didn't think they split other proton environments
Original post by M.Branson98
According to wikipedia, it would be called benzyl benzoate.


Why though..?
Original post by tcameron
yeah I didn't think we included them either because they always are classed as singlets in the nmr spectra so didn't think they split other proton environments


the only hard thing of splitting is CH3-CH2-CH3 which they ask once in this spec only, and never in the last spec i think.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you