CCL:G: What settings should I use in G09W to prevent the breaking of a bond?



 Sent to CCL by: "Gabriela  Arias" [gabriela.ariasdelarosa[-]gmail.com]
 Hello everyone:
 I am doing an optimization and frequency calculation in Gaussian09 to obtain the
 Raman and Infrared spectra of cysteine. In the output, the bond between the
 thiol group and the adjacent carbon is broken, which is wrong. What can I do to
 prevent this bond from breaking? These are the settings that I am using:
 %nprocshared=2
 # opt=tight freq=raman b3lyp/6-311+g geom=connectivity
 Title Card Required
 -1 1
  C                 -2.18907515    2.08528252   -2.35362466
  C                 -2.51526953    1.22134909   -1.12122202
  O                 -2.82257852    1.77040643   -0.03142030
  N                 -0.74900832    2.37936285   -2.37861038
  H                 -0.23470752    1.52307575   -2.42622442
  H                 -0.53719378    2.94035858   -3.17887183
  O                 -2.46894955   -0.20480359   -1.21525919
  C                 -2.57949898    1.32244966   -3.63317742
  H                 -2.02919712    0.40622247   -3.68412445
  H                 -2.35285743    1.92271509   -4.48945717
  H                 -2.73937700    3.00150971   -2.30267762
  C                 -4.08814042    1.01436550   -3.60700190
  H                 -4.35940892    0.48434527   -4.49604181
  H                 -4.63844227    1.93059270   -3.55605487
  S                 -4.46517029    0.01579310   -2.18253651
  H                 -5.74849515   -0.24627848   -2.16027033
  1 2 1.0 4 1.0 8 1.0 11 1.0
  2 3 2.0 7 1.0
  3
  4 5 1.0 6 1.0
  5
  6
  7
  8 9 1.0 10 1.0 12 1.0
  9
  10
  11
  12 13 1.0 14 1.0 15 1.0
  13
 Best regards and thanks for your help,
 Gabriela