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Organic chemistry hybridization and bond angles

  1. Jan 27, 2015 #1
    1. The problem statement, all variables and given/known data
    upload_2015-1-27_7-20-46.png

    Determine the hybridization of the atoms labeled A, B and C in the molecule and the bond angles
    around them.
    2. Relevant equations

    N/A

    3. The attempt at a solution


    A. Normally, I would say it is sp3 for oxygen since there are 4 groups attached to it including the lone pairs. However because it is attached to an sp2 carbon; the lone pair could de-localize and the charge spread. Thus I would think the O's hybridization is actually sp2. Also, I would say the bond angles are less than 109.5 (I don't know if there is an actual or absolute value) because a tetrahedral arrangement has this bond angle but the lone pairs push the bond angles closer together than a tetrahedral bond angle?

    B. Since it is bonded to 3 groups including it's lone pair, and has a double bond, I would say sp2? Bond angle less than 120 degrees since it is bent but greater than 109.5 because it's not tetrahedral?

    C. Sp3 since the N is attached to 4 groups including it's lone electrons and is not attached to an sp2 carbon which could de-localize any charges. Bond angles would be 109.5 because it is in a tetrahedral arrangement?

    Thanks in advance for the help.
     
  2. jcsd
  3. Jan 27, 2015 #2

    Quantum Defect

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    For atoms in the first complete row, count up the number of bonding atoms and lone pairs. This will tell you what the hybridization is.

    4: sp^3; 3: sp^2, 2: sp

    A: two lone pairs, and two bonded atoms. 4 => sp3 I can see how you might think that there is de-localization between the aryl ring and the O, but O's valence is filled, it cannot have a double bond going to it. C-O-C bond angle > 109.5 degrees (lone pairs on oxygen repel each other and the bonding pairs)

    B: one lone pair, two bonded atoms. 3 => sp2 N-N-C bond angle < 120 degrees (lone pair repels the bonding pairs)

    C:eek:ne lone pair, three bonded atoms 4 => sp3. C-N-C bond angles < 109.5 degrees (lone pair repels the bonding pairs)
     
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