structural formula of nicotine:

                 H   H
                  \ /
              H    C -- H  H
             /     |      /
       N == C      N --- C -- H
      /      \     |     |
H -- C        C -- C     C -- H
      \\     //   /  \ /  \
       C -- C    H    C    H
      /      \       / \
     H        H     H   H

            nicotine
            (C10H14N2)