The Student Room Group

Scroll to see replies

Reply 1040
Original post by jannattulfirdaus
hey guys,
im new but i was wondering if anyone can help me with this question...
6) step by step to make mayonaise and...
how long it takes to sepearate

?

I've never seen that anywhere, is it an F324 question? What paper is it.
Reply 1041
Original post by D4rth
?

I've never seen that anywhere, is it an F324 question? What paper is it.


Hi, I think she is trolling!

Want to revise :smile:
Reply 1042
Original post by jannattulfirdaus
hey guys,
im new but i was wondering if anyone can help me with this question...
6) step by step to make mayonaise and...
how long it takes to sepearate


I'll give you my mayonnaise if you want :cool:
Reply 1043
Original post by otrivine
Hi, I think she is trolling!

Want to revise :smile:

Sure, you start, I'll have to do the best I can, haven't started revision yet.
Reply 1044
Original post by D4rth
Sure, you start, I'll have to do the best I can, haven't started revision yet.


no worries :smile:

Describe electrophilic substitution in words (4)
Reply 1045
Original post by otrivine
no worries :smile:

Describe electrophilic substitution in words (4)

So you start with the hardest thing! :P *Grabs textbook*

Substitution reaction when an electrophile (accepts a pair of electrons to form a dative covalent bond) is attracted to an electron rich centre and accepts a pair of electrons to form a new covalent bond. Something is also removed as it's substitution.

Q: Compare the relative relative reactivity of bromine with cyclohexene and benzene (8)
Reply 1046
Original post by D4rth
So you start with the hardest thing! :P *Grabs textbook*

Substitution reaction when an electrophile (accepts a pair of electrons to form a dative covalent bond) is attracted to an electron rich centre and accepts a pair of electrons to form a new covalent bond. Something is also removed as it's substitution.

Q: Compare the relative relative reactivity of bromine with cyclohexene and benzene (8)


Sorry :redface: but good your answer is partially correct!


1) Bromine reacts more readily with cyclohexene than benzene. This is because cyclohexene contains pie-localised electrons sited above and below the plane of the carbon atom. The pi bond is rich in electron density, once the bromine appraches the double bond (C=C) in cyclohexene an electrophilic addition mechanism takes place, as the bromine molecule approaces the pie electron (bond) repels (in double sited above and below the carbon ring) the bromine molecule induces a dipole, forming Br deta+ and bromine deta -. The bromine that is more negative is because both of the electrons move to the bromine which makes it negatively charged and the type of bond breaking is heterolytic fission, the postively deta charged bromine is bonded to the carbon atom, the negatively charged bromine atom is attracted to the postively charged carbocation forming a new covalent bond. This shows that the cyclohexene has a higher (pie) electron density and has pie localised electron that can depolorise the bromine molecule.


When benzene reacts with bromine no reaction takes place under normal conditions this is because benzene has pie delocolased electrons, is a stable molecule, has insufficnet pie electron density and less/no depolarisation of bromine molecule and hence, a halogen carrier is needed for reaction to take place.
Reply 1047
Original post by otrivine
Sorry :redface: but good your answer is partially correct!


1) Bromine reacts more readily with cyclohexene than benzene. This is because cyclohexene contains pie-localised electrons sited above and below the plane of the carbon atom. The pi bond is rich in electron density, once the bromine appraches the double bond (C=C) in cyclohexene an electrophilic addition mechanism takes place, as the bromine molecule approaces the pie electron (bond) repels (in double sited above and below the carbon ring) the bromine molecule induces a dipole, forming Br deta+ and bromine deta -. The bromine that is more negative is because both of the electrons move to the bromine which makes it negatively charged and the type of bond breaking is heterolytic fission, the postively deta charged bromine is bonded to the carbon atom, the negatively charged bromine atom is attracted to the postively charged carbocation forming a new covalent bond. This shows that the cyclohexene has a higher (pie) electron density and has pie localised electron that can depolorise the bromine molecule.


When benzene reacts with bromine no reaction takes place under normal conditions this is because benzene has pie delocolased electrons, is a stable molecule, has insufficnet pie electron density and less/no depolarisation of bromine molecule and hence, a halogen carrier is needed for reaction to take place.

Good!
Reply 1048
I've been at this questions for ages with no clue on how to move forward, could someone help please? :smile:

Question 1.e) http://www.ocr.org.uk/Images/79471-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Thanks!
Reply 1049
Original post by XiLE
I've been at this questions for ages with no clue on how to move forward, could someone help please? :smile:

Question 1.e) http://www.ocr.org.uk/Images/79471-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Thanks!

It's pretty simple once you see what you need to do. If you look at the structure they give, it's the same answer but if you look at the carbon between the NH and C=O bond on the top and bottom if the structure, you add on the R group.

It's basically the molecules forming bonds with themselves, just imagine another molecule attaching to the bottom of itself.

I know I didn't explain very well... but I hope I kind of explained.
(edited 10 years ago)
Reply 1050
Original post by D4rth
It's pretty simple once you see what you need to do. If you look at the structure they give, it's the same answer but if you look at the carbon between the NH and C=O bond on the top and bottom if the structure, you add on the R group.

It's basically the molecules forming bonds with themselves, just imagine another molecule attaching to the bottom of itself.

I know I didn't explain very well... but I hope I kind of explained.




Describe transesterification (3)
I've got a question for you guys which Is the stronger base and why, phenyl amine or hexan1amine?
:tongue:
Reply 1052
Original post by Patel3000
I've got a question for you guys which Is the stronger base and why, phenyl amine or hexan1amine?
:tongue:

hexan-1-amine because it readily accepts a proton and can undergo multiple nucleophilic substitution.
Reply 1053
Original post by otrivine
Describe transesterification (3)

This is esterification but between Glycerol (Propane-1,2,3-triol) and a long fatty chain carboxylic acid which is unsaturated and it is trans (z) about the c=c double bond.

Glycerol undergoes esterification with 3 molecules of the fatty acid eliminating water under a Conc. H2SO4 catalyst.
Reply 1054
Original post by D4rth
This is esterification but between Glycerol (Propane-1,2,3-triol) and a long fatty chain carboxylic acid which is unsaturated and it is trans (z) about the c=c double bond.

Glycerol undergoes esterification with 3 molecules of the fatty acid eliminating water under a Conc. H2SO4 catalyst.


No transesterification is involved in the process of making biodisel ? or am i WRONG
Original post by Zaphod77


To get an A you need 480/600 over the whole A-level. You have 260+109+45(coursework)=414. This means that you need 66/90UMS in F324. To get an A* you need 270/300 for the A2 year - currently at A2 you have 109+45=154, so you would need 116/90 UMS for an A* in F324, which is impossible, sorry. You should be able to get an A, just work hard and you'll get there!


how did you know 35/40 was 45 ums ?
Does anyone have any combined techniques questions (IR, mass spec and NMR)? I can't find more than a few on the internet and i've already done the ones in the book :s-smilie:
Reply 1057
Original post by otrivine
No transesterification is involved in the process of making biodisel ? or am i WRONG



Explain why it is bad to make a racemic drug [3]



How do drug companies make a drug with no optical isomers? [3]
Reply 1058
Original post by Zzzyax
Explain why it is bad to make a racemic drug [3]



How do drug companies make a drug with no optical isomers? [3]


1) This is because there are 2 optical isomers , one of the isomers is pharmacologically active and has the good effect such as thalidomide, one of the isomer helps to treat morning sickness but the other isomer could have potentially adverse side effects such as in thalidomide the isomer that is harmful is that it leads to deformities in babies.

2) By different methods, seprating isomer such as using enzymes as biological catalysts, chiral pool synthesis, using transition metal complexes.
Reply 1059
Original post by otrivine
1) This is because there are 2 optical isomers , one of the isomers is pharmacologically active and has the good effect such as thalidomide, one of the isomer helps to treat morning sickness but the other isomer could have potentially adverse side effects such as in thalidomide the isomer that is harmful is that it leads to deformities in babies.

2) By different methods, seprating isomer such as using enzymes as biological catalysts, chiral pool synthesis, using transition metal complexes.


1)Be more specific
other optical isomers could have unwanted side effects
increased dosage required
cost of seperation

2) good, but do you know what chiral pool synthesis is, or how transition metals are used

Latest