Notices
Results 1 to 7 of 7

Thread: Finding Transition state structures

  1. #1 Finding Transition state structures 
    Forum Freshman
    Join Date
    Aug 2005
    Posts
    6
    I have no one to turn to for help. I don't even know how to frame the right questions to ask....I feel so quizzed!

    Is it true that intermediates have 'memory'. When you throw an intermediate into a reaction, you actually produce a product there wasn't there based on what the intermediate was produced from originally. In the equilibrium mixture, you will end up with the some products, some orignal reactants of another reaction and the intermediate (which I believe is long lived species of any reaction).

    Is it true that the intermediate has memory because it is so close to its transition state. How does this 'memory' operate? HELP!!!!!!!!!!!!

    Does it mean that if the intermediate is stable and thus lower in energy than the original reactants, the activation energy for such a reaction is thus lower since the transition state is closer to the intermediate than the reactants?????


    Please, any website or tutorial or title or journal or title of book will be tremendously useful!


    Reply With Quote  
     

  2.  
     

  3. #2  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,168
    Can you give an example of the sort of reaction you are talking about? That might help us understand your question a little more precisely.


    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Aug 2005
    Posts
    6
    I don't have a reaction at the moment on which to depend on. But I do know that I need a tutorial on the basics!!!!!!!!!!111
    Reply With Quote  
     

  5. #4  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,168
    Science, I still need something more than what you have offered so far. You aren't making much sense.
    Molecular memory, in the sense in which you seem to be talking about it, sounds very much like homeopathy, which many would consider a pseudo-science.
    You state "the intermediate, which I believe is long lived species of any reaction". This is thoroughly confusing. Surely the long lived species of any reaction is the end product(s). An intermediate is so named because it is intermediate between starting products and end products. It is not long lived: it is transitional. What am I misunderstanding in your questions?
    Reply With Quote  
     

  6. #5  
    j
    j is offline
    Forum Bachelors Degree
    Join Date
    Mar 2005
    Posts
    431
    Something is nibbling at the back of my brain about this ...


    What types of 'reactants' and 'intermediates' are you talking about? Organic, inorganic? Non-metals or metals? Alkali, alkali earth or transition metals?

    If this is for a course, what course is it?

    Are you talking about advanced organic synthesis?
    Why do they want us to believe Conspiracy Theories?
    Reply With Quote  
     

  7. #6 Re: Finding Transition state structures 
    Him
    Him is offline
    Forum Sophomore Him's Avatar
    Join Date
    Aug 2005
    Posts
    181
    Must agree, intermediate comes with the context. they can be longer lived, the borderline with end product sometimes difficult to determine and again depending on the context. Long or short I do not think this is essential for your question. There in opnion the answer stays the same, only the one is experimental more applicable.

    Quote Originally Posted by science
    Is it true that intermediates have 'memory'. When you throw an intermediate into a reaction, you actually produce a product there wasn't there based on what the intermediate was produced from originally.

    (throwing an intermediate into an reaction so it must be ‘long’ lived)

    How the intermediate was fabricated, which you throw into your does not have any effect. (If chemical structure and physical formulation is the same). However it basic chemical structure is linked with it is starting products, so this process you described can happen. But I wouldn’t call memory, it is just a possibility among others depending on your current conditions.

    Quote Originally Posted by science

    Is it true that the intermediate has memory because it is so close to its transition state. How does this 'memory' operate? HELP!!!!!!!!!!!!
    Does it mean that if the intermediate is stable and thus lower in energy than the original reactants, the activation energy for such a reaction is thus lower since the transition state is closer to the intermediate than the reactants?????
    Intermadiates very close to the transition state will be very short lived, as the transition state itself. but still let us presume you can throw them into your reaction their outcome is purely dependable on the energy profile of the reaction itself and the energy in your system. Not of how you created the intermediated.

    But I doubt I’m not telling anything new here, so maybe you need to clarify question (as asked above), because this is described in the most basic chemical books.
    he who forgets...will be destined to remember (Nothing Man - Pearl Jam)
    Reply With Quote  
     

  8. #7  
    Forum Sophomore
    Join Date
    Oct 2005
    Posts
    177
    I really don't know what yuo are talking about.

    But I could imagine one type of "memory" assuming the 'same' intermediate is onvolved, assuming the intermediate could be isolated.

    Assume this reaction, and the intermediate has the asterisk:

    A + B -> AB* -> C + D ...or.... A + B -> AB* -> F

    If this reaction were run in different solvents, and not the gas phase, then AB* could look different, and these differences could be lost in common shorthand notation:

    AB* (THF)n
    AB* (benzene)n
    AB* (H2O)n
    AB* (DMSO)n
    etc

    where the solvent molecules play a role in stabilizing the intermediate. Depending on how well the solvent molecules donate or withdraw electrons from orbitals of the intermediate AB*, this could the stability of the intermediate and whether the ultimate pathway follows a decomposition to C + D , or merges to form F.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •