Hey there Sign in to join this conversationNew here? Join for free

Optical isomerism of complex ions (F325)

Announcements Posted on
Study Help needs new mods! 14-04-2014
Post on TSR and win a prize! Find out more... 10-04-2014
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    A question I've come across:

    Describe the types of stereoisomerism found in transition metal complexes.
    Use suitable examples to illustrate your answer.

    So for optical isomerism, I drew two [Ni(en)_3]^2+ enantiomers. (I think!)
    (Ni ion with three H_3NCH_2CH_2NH_3 bidentates)

    The marks scheme says:
    (Optical) + examples (must be 3-d drawings)
    Rotate plane polarised light (by same number of
    degrees) in opposite directions
    Non-superimposable mirror images
    NB If use H_3NCH_2CH_2NH_3 penalise only once



    Why can't I use H_3NCH_2CH_2NH_3? And what could I use instead? Thanks!
    • 19 followers
    Offline

    ReputationRep:
    (Original post by whotosee)
    A question I've come across:
    Describe the types of stereoisomerism found in transition metal complexes.
    Use suitable examples to illustrate your answer.
    So for optical isomerism, I drew two [Ni(en)_3]^2+ enantiomers. (I think!)
    (Ni ion with three H_3NCH_2CH_2NH_3 bidentates)

    The marks scheme says:
    (Optical) + examples (must be 3-d drawings)
    Rotate plane polarised light (by same number of
    degrees) in opposite directions
    Non-superimposable mirror images
    NB If use H_3NCH_2CH_2NH_3 penalise only once



    Why can't I use H_3NCH_2CH_2NH_3? And what could I use instead? Thanks!
    Please quote the question exactly, including previous parts of the same question and the markscheme.

    And the formula you have written for 'en' is incorrect, they are NH2 groups.
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (Original post by charco)
    Please quote the question exactly, including previous parts of the same question and the markscheme.

    And the formula you have written for 'en' is incorrect, they are NH2 groups.
    I got the question from this question pack someone else put up so I'm not sure if it's the whole question:

    Question:

    Describe the types of stereoisomerism found in transition metal complexes.
    Use suitable examples to illustrate your answer.
    [8]
    Quality of Written Communication [1]
    [Total 9 marks]

    Marks scheme:
    (Cis/trans) + Examples (must be 3-d drawings) 2
    Correctly labelled as cis and trans (allow this mark if diagrams are planar) 1
    Cis has same atoms at 90° + Trans has same atoms at
    180° (need reference to bond angles for mark) 1
    (Optical) + examples (must be 3-d drawings) 2
    Rotate plane polarised light (by same number of
    degrees) in opposite directions 1
    Non-superimposable mirror images 1
    NB If use H3N CH2 CH2 NH3 penalise only once

    Any example which show the principle of cis/trans isomerism and optical
    isomerism are fine but, all diagrams must be 3-d. The shapes shown in the
    previous question are allowed for octahedral or tetrahedral. For square planar
    complexes used to illustrate cis/trans isomerism the following illustrations
    are fine. For optical isomerism, there must be a mirror line and the isomers must
    be non-superimposable object/mirror images.
    M M M M

    QWC – to be awarded for the correct use of scientific
    terms, to include at least 3 of the following:
    Cis & trans, optical, plane, polarised, non-superimposable,
    mirror images, geometric, bidentate,
    ligand, octahedral, square planar, tetrahedral 1

    And thanks for the 'en' formula thing!
    (The mark scheme has it wrong too for some reason :mad:)
    • 3 followers
    Offline

    ReputationRep:
    Different notation is used for the isomers you would have drawn. These are right hand and left hand versions of a propeller. You should be able to spot it in the diagrams.

    The isomers are ∆ and Λ, there is a bit about it on this link:

    http://ww2.chemistry.gatech.edu/~wil..._complexes.pdf
    • 16 followers
    Offline

    ReputationRep:
    (Original post by whotosee)
    I got the question from this question pack someone else put up so I'm not sure if it's the whole question:

    Question:

    Describe the types of stereoisomerism found in transition metal complexes.
    Use suitable examples to illustrate your answer.
    [8]
    Quality of Written Communication [1]
    [Total 9 marks]

    Marks scheme:
    (Cis/trans) + Examples (must be 3-d drawings) 2
    Correctly labelled as cis and trans (allow this mark if diagrams are planar) 1
    Cis has same atoms at 90° + Trans has same atoms at
    180° (need reference to bond angles for mark) 1
    (Optical) + examples (must be 3-d drawings) 2
    Rotate plane polarised light (by same number of
    degrees) in opposite directions 1
    Non-superimposable mirror images 1
    NB If use H3N CH2 CH2 NH3 penalise only once

    Any example which show the principle of cis/trans isomerism and optical
    isomerism are fine but, all diagrams must be 3-d. The shapes shown in the
    previous question are allowed for octahedral or tetrahedral. For square planar
    complexes used to illustrate cis/trans isomerism the following illustrations
    are fine. For optical isomerism, there must be a mirror line and the isomers must
    be non-superimposable object/mirror images.
    M M M M

    QWC – to be awarded for the correct use of scientific
    terms, to include at least 3 of the following:
    Cis & trans, optical, plane, polarised, non-superimposable,
    mirror images, geometric, bidentate,
    ligand, octahedral, square planar, tetrahedral 1

    And thanks for the 'en' formula thing!
    (The mark scheme has it wrong too for some reason :mad:)
    MS got it right..it says penalise if its NH3
    Just ruined the joy of thinking examiner gets things wrong too :rolleyes:
    • 16 followers
    Offline

    ReputationRep:
    (Original post by JMaydom)

    The isomers are ∆ and Λ, there is a bit about it on this link:
    That's not in our syllabus
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (Original post by arvin_infinity)
    MS got it right..it says penalise if its NH3
    Just ruined the joy of thinking examiner gets things wrong too :rolleyes:
    Ah right! That makes sense now
    Thank you!

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?

    this is what you'll be called on TSR

  2. this can't be left blank
    this email is already registered. Forgotten your password?

    never shared and never spammed

  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By completing the slider below you agree to The Student Room's terms & conditions and site rules

  2. Slide the button to the right to create your account

    Slide to join now Processing…

    You don't slide that way? No problem.

Updated: June 9, 2012
Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.