Data type: null
_chemical_formula_moiety 'C18 H25 N O3' _chemical_formula_sum 'C18 H25 N O3' _chemical_formula_weight 303.40
Example 1 - based on data set TOZ of Willis, Beckwith & Tozer [(1991). Acta Cryst. C47, 2276-2277].
_chemical_formula_iupac '[Mo (C O)4 (C18 H33 P)2]' _chemical_formula_moiety 'C40 H66 Mo O4 P2' _chemical_formula_structural '((C O)4 (P (C6 H11)3)2)Mo' _chemical_formula_sum 'C40 H66 Mo O4 P2' _chemical_formula_weight 768.81
Example 2 - based on data set 9597gaus of Alyea, Ferguson & Kannan [(1996). Acta Cryst. C52, 765-767].
_chemical_formula_ items specify the composition and chemical properties of the compound. The formula data items must agree with those that specify the density, unit-cell and Z values. The following rules apply to the construction of the data items _chemical_formula_analytical, *_structural and *_sum. For the data item *_moiety the formula construction is broken up into residues or moieties, i.e. groups of atoms that form a molecular unit or molecular ion. The rules given below apply within each moiety but different requirements apply to the way that moieties are connected (see _chemical_formula_moiety). 1. Only recognized element symbols may be used. 2. Each element symbol is followed by a 'count' number. A count of '1' may be omitted. 3. A space or parenthesis must separate each cluster of (element symbol + count). 4. Where a group of elements is enclosed in parentheses, the multiplier for the group must follow the closing parentheses. That is, all element and group multipliers are assumed to be printed as subscripted numbers. [An exception to this rule exists for *_moiety formulae where pre- and post-multipliers are permitted for molecular units]. 5. Unless the elements are ordered in a manner that corresponds to their chemical structure, as in _chemical_formula_structural, the order of the elements within any group or moiety depends on whether or not carbon is present. If carbon is present, the order should be: C, then H, then the other elements in alphabetical order of their symbol. If carbon is not present, the elements are listed purely in alphabetic order of their symbol. This is the 'Hill' system used by Chemical Abstracts. This ordering is used in _chemical_formula_moiety and _chemical_formula_sum.