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POST-EXAM CHAT: OCR Chemistry- Rings, Polymers and Analysis - F324 thread Watch

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    (Original post by Noble.)
    The point is that there isn't going to be a halogen carrier in the reaction mixture, so it's impossible for that to be formed. The question asked what impurity could be formed in the reaction, it's impossible for that to be formed.

    It will reduce carboxylic acids, it says that they do in both the Cambridge book and the Smith & Older book.
    NaBH4 will only reduce carboxylic acids under certain conditions: (quoted):
    Oxidation of NaBH4 with iodine in tetrahydrofuran gives the BH3-THF complex, which can reduce carboxylic acids. Likewise, the NaBH4-MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols, for instance, benzyl benzoate to benzyl alcohol.

    It won't do it by itself.
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    I'll ask again as nobody is responding:
    halogenalkane with peptide bond in one of them (can't remember whether aspirin or paracetamol), would it work to form a tertiary amine?
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    I felt that some of the questions weren't detailed enough. Don't know about you guys, but some of the questions confused me. As if there wasnt any direct answer but you had to think alot which took a lot of time. If i had 15 minutes more..maybe 20...I wouldve done way better...Guaranteed.
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    (Original post by andy892)
    NaBH4 will only reduce carboxylic acids under certain conditions: (quoted):
    Oxidation of NaBH4 with iodine in tetrahydrofuran gives the BH3-THF complex, which can reduce carboxylic acids. Likewise, the NaBH4-MeOH system, formed by the addition of methanol to sodium borohydride in refluxing THF, reduces esters to the corresponding alcohols, for instance, benzyl benzoate to benzyl alcohol.

    It won't do it by itself.
    You're not going to get it wrong by putting NaBH4 though, as it's perfectly acceptable for this specification.
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    (Original post by JordanCarroll)
    you know what was great?
    the massive absence of green chemistry :rolleyes:
    You know what you're absolutley on the dot. Normally I hate green chemistry but looking at this paper...I miss greeen chemistry like a *****.
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    (Original post by Noble.)
    You're not going to get it wrong by putting NaBH4 though, as it's perfectly acceptable for this specification.
    Well, of course, I would be glad if that were to be the case as I would gain the marks - but you would have also needed to state those extra bits in the answer to gain the marks probably, and that is quite complex, definitely beyond the scope of this course. It isn't mentioned in the textbook.
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    (Original post by SPF100)
    The question specifically said name or list the sequence of amino acids, so sorry but you are wrong.
    i went back through and realised i had just wrote valine! quickly changed that :p:
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    (Original post by andy892)
    Well, of course, I would be glad if that were to be the case as I would gain the marks - but you would have also needed to state those extra bits in the answer to gain the marks probably, and that is quite complex, definitely beyond the scope of this course. It isn't mentioned in the textbook.
    Considering there's absolutely no mention of using anything other than NaBH4 when reducing a carboxylic acid in two of the books for the course (one of them written by the chief examiner) I doubt they're looking for anything more than just NaBH4.
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    (Original post by Bucknasty)
    You know what you're absolutley on the dot. Normally I hate green chemistry but looking at this paper...I miss greeen chemistry like a *****.
    dont say that man!
    DON'T SAY IT!!!
    :eek:
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    if i had a scanner i would persuade my teacher to let me have the paper and upload it :/
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    ahhhh I ran out of time too and that OH on the aldehyde group confused me My school arent even gonna let us retake this unit aaah
    azo dyes n the first pages n stuff were a treat though
    Completely ran out of time for the last question
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    (Original post by Noble.)
    You're not going to get it wrong by putting NaBH4 though, as it's perfectly acceptable for this specification.
    I put NaBH4 as well. We're supposed to know about the reduction of aldehydes, but not the reduction of carboxylic acids. Hopefully I won't be penalised! I should have put something much more simple like an alcohol - didn't think of esterification!

    Also, for the very last one, would acidified potassium dichromate be acceptable? - I was thinking the -OH group on the phenol would become oxidised to become a ketone, but then I realised that the carbon would be making 4 bonds (2 with two other carbon atoms in the benzene ring and 2 with the oxygen atom) so it wouldn't have a delocalised electron in the p-orbital. So I crossed out the circle in the middle of the benzene ring. I think I've lost 2 marks there :p:
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    (Original post by sa121)
    ahhhh I ran out of time too and that OH on the aldehyde group confused me My school arent even gonna let us retake this unit
    why do they have any say in that? evil people
    my school dont mind as long as you supply the £££
    if you reallllyyy want to cant you just retake it at another place? :p:
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    45-47 for an A i think, what does every1 else think?
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    (Original post by JordanCarroll)
    i went back through and realised i had just wrote valine! quickly changed that :p:
    :facepalm: I just wrote valine, and because I was messing around with the other questions, I didn't have enough time. Was that worth 1 mark?
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    (Original post by JordanCarroll)
    why do they have any say in that? evil people
    my school dont mind as long as you supply the £££
    if you reallllyyy want to cant you just retake it at another place? :p:
    Well, they recomment you don't do it because the June module is so huge and they say you should retake AS modules....I duno..I guess if I persuaded them into it they would let me! Yeah retaking it somewhere else is also an option...see what I get in March though hey?
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    recommend * LOL
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    NaBH4 is lame ffs :sigh: cant even reduce a ******* carboxylic acid :sigh:
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    (Original post by JordanCarroll)
    NaBH4 is lame ffs :sigh: cant even reduce a ******* carboxylic acid :sigh:
    Tell me about it... so weak; it's PATHETIC.
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    (Original post by _lynx_)
    :facepalm: I just wrote valine, and because I was messing around with the other questions, I didn't have enough time. Was that worth 1 mark?
    yeah sounds like a one-marker, meh
    (Original post by sa121)
    Well, they recommend you don't do it because the June module is so huge and they say you should retake AS modules....I duno..I guess if I persuaded them into it they would let me! Yeah retaking it somewhere else is also an option...see what I get in March though hey?
    yeah i see the june chem is gona be a beast :p:
    i really want march to hurry the hell up!!!
 
 
 
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