17 Representation of Structural Formulas by 02aYHwR

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									Solomons/SoloCh01

1.17 REPRESENTATION OF STRUCTURAL FORMULAS


                                                                        H       H       H
                                                                H       C       C       C    O   H
                                                                        H       H       H
             Ball-and-stick model                                        Dash formula

                 CH3CH2CH2OH                                                                OH

              Condensed formula                                     Bond-line formula

Figure 1.36 Structural formulas for propyl alcohol.

                                                H           H
                      H   H
                    H C O C H       =   H       C       O   C       H       =   CH3OCH3
                      H   H
                                                H           H
                    Dot structure           Dash formula                    Condensed formula


  1.17A Dash Structural Formulas

   1. Atoms joined by single bonds can rotate relatively freely with respect to one
        another.
                                                        H
         H       HH         H                                                       H       H
                                        H       HO          H
             C          C       H or                                or      H           C        O
        H           C       O               C           C                           C        C       H
                                        H           C       H
               H        H                                                   H           HH       H
                                             H          H

    Equivalent dash formulas for propyl alcohol  same connectivity of the atoms

   2. Constitutional isomers have different connectivity and, therefore, must have
        different structural formulas.
   3. Isopropyl alcohol is a constitutional isomer of propyl alcohol.




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Solomons/SoloCh01

                             H                              H    H    H                 H   O    H
                     H       O       H                 H    C    C    C   H         H   C   C    H
                                                  or                          or
             H       C       C       C       H              H H C H
                                                                 O    H
                                                               H
             H H H                        H                        H
  Equivalent dash formulas for isopropyl alcohol  same connectivity of the atoms

   4. Do not make the error of writing several equivalent formulas.


  1.17B Condensed Structural Formulas

             H       H       H       H
       H     C       C       C       C       H             CH3CHCH2CH3 or          CH3CHClCH2CH3
             H       Cl H            H                          Cl

                 Dash formulas                                        Condensed formulas


                 H       H       H                         CH3CHCH3                CH3CH(OH)CH3
         H       C       C       C       H                      OH
                 H       O       H
                                                           CH3CHOHCH3 or            (CH3)2CHOH
                         H
             Dash formulas                                           Condensed formulas

  1.17C Cyclic Molecules

                     H           H
                             C                          CH2
                 H                   H       or                      Formulas for cyclopropane
                         C       C                H2C      CH2
                     H               H



  1.17D Bond-Line Formulas (shorthand structure)

   1. Rules for shorthand structure:
     1) Carbon atoms are not usually shown  intersections, end of each line
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Solomons/SoloCh01

     2) Hydrogen atoms bonded to C are not shown.
     3) All atoms other than C and H are indicated.

                                           H3C          CH2
                                                  CH          CH3
              CH3CHClCH2CH3            =                            =
                                                  Cl                        Cl
                                           H3C          CH2
                                                  CH          CH3
            CH3CH(CH3)CH2CH3 =                                      =
                                                  CH3
                                           H3C          CH2
                                                  N           CH3           N
               (CH3)2NCH2CH3           =                            =
                                                  CH3
                                                                        Bond-line
                                                                        formulas


                          CH2                            H2C    CH2
                                  =              and                    =
                    H2C    CH2                           H2C    CH2


    H3C         CH         CH3
           CH        CH2                                                                     OH
                              =                         CH2=CHCH2OH =
           CH3




       Table 1.5 Kekulé and shorthand structures for several compounds

          Compound                    Kekulé structure              Shorthand structure
                                        H H H H
  Butane, C4H10                       H C C C          C H
                                                                                C        C
                                        H H H H                             C        C

                                        H         H
  Chloroethylene (vinyl                     C C
                                                                                     Cl
  chloride), C2H3Cl                                                              C
                                        H         Cl                        C        Cl




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Solomons/SoloCh01

                                                      H
  2-Methyl-1,3-butadiene                    H H C H   H
  (isoprene), C5H8                            C C C C
                                            H     H   H

                                                   H H
                                                  H    H
                                                    C
                                                H C   C H
  Cyclohexane, C6H12
                                                H C    C H
                                                          C
                                                  H     H
                                                    H H
                                                 H HH H
                                                H C           H H   H H H
                                                       C H H
                                                         H    C   H   C H   H
                                                  H
                                                     C   C    C   C   C   C
                                                H C    C    C   C   C   C   O H
                                                          H
                                                H C    C    H   H   H   H
  Vitamin A, C20H30O                                 C   C H
                                                 H
                                                    H H H



                                                                                                      OH




  1.17E Three-Dimensional Formulas


                                                                                                           H
           H                        H                 H                         H
                                                                                                  H
                       or                                         or                                       C       H
           C       H        H       C                 C       H         H       C             H       C
      H                                 H       Br                                  Br                         H
               H                H                         H                 H
                                                                                                  H
                   Methane                            Bromomethane                                Ethane

                   H                        H                               H                     H
                   C  or                                                                 or
          Br     H       H C Br                                    Br
                                                                            C       I I C Br
                Cl        Cl                                                Cl         Cl
             Bromo-chloromethane                                       Bromo-chloro-iodomethane

Figure 1.37 Three-dimensional formulas using wedge-dashed wedge-line formulas.



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