Page 229 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements
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6.3 S Cl AND SCl
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               represented in a Lewis structure, that is, via a simple double-bonded structure (O=O). The
               triplet ground state requires a molecular orbital description, which is presented in most
               general and inorganic chemistry textbooks.
                  Let’s reflect for a moment on how the chemistry just described compares with the chem-
               istry of the sulfanes described in the last section. Like the sulfane SH groups, the oxygens of
               H O can act as nucleophiles. Like the sulfur atoms within polysulfide chains, the oxygens
                   2
                 2
               in H O can also act as electrophiles. One distinct feature of H O chemistry is of course
                   2
                                                                  2
                                                                    2
                     2
               its potential for oxidation to O . Sulfanes too are prone to oxidation but not to diatomic S ,
                                       2
                                                                                      2
               which is unstable, but rather to medium-sized S rings.
                                                     n
               6.3  S Cl AND SCl  2
                        2
                     2
               Passing chlorine through molten sulfur results in disulfur dichloride (S Cl ), a fuming
                                                                             2
                                                                          2
               orange liquid. Further chlorination leads to sulfur dichloride (SCl ).
                                                                   2
                                           S + 4Cl → 4S Cl  2                     (6.24)
                                                         2
                                            8
                                                   2
                                          S Cl + Cl → 2SCl 2                      (6.25)
                                              2
                                           2
                                                   2
               Taking the first reaction first, we need to first identify the nucleophile and electrophile, that
                                                 −
                                                                            −
               is, what attacks what. Considering that Cl is a much weaker base than HS (which is a
               different way of saying that HCl is a strong acid and H S is a weak one), one of the S
                                                             2                        8
               sulfurs seems likely to be the nucleophile that attacks Cl , kicking out a chloride ion:
                                                            2
                         S                                   S       +         −
                  S  S   S   S  S    Cl   Cl          S  S   S   S   S   Cl  +  Cl  (6.26)
                     S       S                           S       S
               The displaced chloride now attacks an adjacent sulfur, creating the linear-chain molecule
               ClSSSSSSSSCl:
                              S       +                      S
                       S   S  S    S  S   Cl          S   S  S   S   S   Cl
                           S  −    S                      S      S                (6.27)
                             Cl
                                                                  Cl

               One of the internal sulfurs of S Cl linear chain can now act as the nucleophile and attack
                                           2
                                        8
               a second molecule of Cl :
                                   2
                             S                                 S
                         S       S      Cl           −      S       S      Cl
                      S      S      S              Cl  + S     S       S
                         S       S                          S   +   S             (6.28)
                          Cl                                 Cl
                     Cl
                                  Cl                                 Cl
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