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    Is there a straightforward, reliable way of being given a reaction (reactants and products, no intermediates) and deducing whether the reactants underwent: a) hydrolysis; b) dehydration; c) oxidation; d) reduction; e) reduction with addition of an alkyl nucleophile; or f) condensation? I'm talking purely about organic molecules here.

    I know the basic definitions of each, but nonetheless it is often not obvious to me which change has occurred. Is there any reliable way to look at the structures and find out?
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    (Original post by Big-Daddy)
    Is there a straightforward, reliable way of being given a reaction (reactants and products, no intermediates) and deducing whether the reactants underwent: a) hydrolysis; b) dehydration; c) oxidation; d) reduction; e) reduction with addition of an alkyl nucleophile; or f) condensation? I'm talking purely about organic molecules here.

    I know the basic definitions of each, but nonetheless it is often not obvious to me which change has occurred. Is there any reliable way to look at the structures and find out?
    Yes, understand/learn the outcome of each reaction. You can easily tell which has happened as the product will almost always be different for each reaction
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    (Original post by JMaydom)
    Yes, understand/learn the outcome of each reaction. You can easily tell which has happened as the product will almost always be different for each reaction
    Yeah, so my question is, what to look for in the products (compared with the reactants) to figure out which reaction has occurred.

    I think I might be able to suggest what to look for in the case of reduction/reduction by alkyl nucleophile:

    Simply put, you will gain 1 or more H atoms during reduction to your overall molecule. The general definition also says "loss of O" is reduction, but in organic terms every example I look at seems to involve H atoms being added (often accompanied with dropping from a triple or double bond to a highly electronegative element, e.g. O, S or N, to a double or single bond). Meanwhile, reduction with addition of an alkyl nucleophile is the same, but instead of H atoms being added, I look for signs that the bonds to highly electronegative elements have dropped in number and that a new carbon chain is present substituted on the C which had been (maybe still is) attached to the highly electronegative element(s). Is this correct? If so, then that means d) and e) are dealt with.

    And oxidation? You will decrease the number of bonds to a less electronegative element (e.g. lose H, or decrease bonds with/lose metals or Si), or increase the number of bonds to a more electronegative element (e.g. O, S, N, P, F, Cl, Br, I, ).

    The problem really is in hydrolysis, condensation and dehydration - how do I spot these?
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    (Original post by Big-Daddy)
    Yeah, so my question is, what to look for in the products (compared with the reactants) to figure out which reaction has occurred.

    I think I might be able to suggest what to look for in the case of reduction/reduction by alkyl nucleophile:

    Simply put, you will gain 1 or more H atoms during reduction to your overall molecule. The general definition also says "loss of O" is reduction, but in organic terms every example I look at seems to involve H atoms being added (often accompanied with dropping from a triple or double bond to a highly electronegative element, e.g. O, S or N, to a double or single bond). Meanwhile, reduction with addition of an alkyl nucleophile is the same, but instead of H atoms being added, I look for signs that the bonds to highly electronegative elements have dropped in number and that a new carbon chain is present substituted on the C which had been (maybe still is) attached to the highly electronegative element(s). Is this correct? If so, then that means d) and e) are dealt with.

    And oxidation? You will decrease the number of bonds to a less electronegative element (e.g. lose H, or decrease bonds with/lose metals or Si), or increase the number of bonds to a more electronegative element (e.g. O, S, N, P, F, Cl, Br, I, ).

    The problem really is in hydrolysis, condensation and dehydration - how do I spot these?
    it would be easier to explain if you gave an example. Give a example molecule....
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    (Original post by JMaydom)
    it would be easier to explain if you gave an example. Give a example molecule....
    First things first. Does elimination count as a form of reduction? (Seeing as it involves loss of a bond to a more electronegative molecule?)

    As for a molecular example of hydrolysis, I've attached an example reaction.

    But it's the principle I'm looking for - how would we spot reactions in general are cases of hydrolysis (as opposed to say reduction, which is what the right-hand product looks a bit like).

    Edit: A better example to represent my difficulties would be this: http://www.c3l6.org/files/C3L6_student_exam_2012.pdf Question 2, a, part vii.) By my definition of reduction, requiring both a decrease in the number of bonds to more electronegative elements and an increase in the number of bonds to less electronegative elements, this admittedly does not fit the bill - but how was I supposed to tell this reaction was hydrolysis?
    Attached Files
  1. File Type: pptx ChemistryDrawing2.pptx (37.2 KB, 88 views)
 
 
 
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