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Easy Way to Determine R, S Configuration

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    Easy Way To determine R, S

    Configuration..Prepared by : Mohit R. Rokad

    ([email protected])

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    Hi, Friends....

    Here is an easy way to

    detect whether thecompound is having R

    configurationor S configuration...

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    You have to just remember the sequence of numbering ofgroups.... that is

    1. The higher the atomic number of the immediate substituentatom, the higher the priority.For example, H < C < N < O < Cl. (Different isotopes ofthe same element are assigned a priority according to theiratomic mass.)2. If two substituents have the same immediate substituentatom,evaluate atoms progressively further away from the chiralcenter until a difference is found.For example, CH3 < C2H5 < ClCH2 < BrCH2 < CH3O.

    3. If double or triple bonded groups are encountered assubstituents, they are treated as an equivalent set of single-bonded atoms.For example, C2H5 < CH2=CH < HCC

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    identify the chirality center(s) assign the relative priorities

    STEP 1STEP 2

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    Now The Tricky Part Comes....

    ^_^ 1 2 3 4

    1

    2

    3

    4

    R

    S

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    For any example,

    Suppose we are having no. like this...

    3

    4

    2

    1

    So.. now we can directly say that it is..... R Configuration.....

    Lets see how can its possible to define it as R without orientating it in a

    sequence of 1,2,3,4......

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    Given structure is......

    3

    4

    2

    1

    So... At First Look at horizontal line....

    i.e.

    3 2

    Now... Look For the 3rd no. raw and 2nd column in table

    3

    I am talking about this one.....

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    2nd column

    3rd raw

    As We know that RED

    represents R and Blue is

    forS.....

    Now its time to see the

    vertical line from

    structure....

    3

    4

    2

    1

    we can see that the vertical line is having 4 and 1 no. on its ends..

    and the higher no. is 4. You can see that its on upper side and from

    the box you can see that upper side arrow is RED, Which shows R

    configuration.....

    So.... YES... Its R Configuration......... Lets have a little practice..

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    3

    4

    1

    4

    look at the box... that is 1st raw and 2rd column

    2nd column

    1st raw

    Now in vertical line we can see that 3 and 4 no. are there... and 4 > 3... and 4 is on

    lower side.... Now in box lower sided arrow is BLUE.. And BLUE colour is for S

    configuration.. So Its S configuration

    Practice example : 1

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    1

    4

    3

    2

    look at the box... that is 1st raw and 3rd column

    3nd column

    1st raw

    Now in vertical line we can see that 2 and 4 no. are there... and 4 > 2... and 4 is on

    upper side.... Now in box upper sided arrow is BLUE.. And BLUE colour is for S

    configuration.. So Its S configuration

    Practice example : 12

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    Enjoy This Tricky Method.......


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