JChem Base offers sophisticated chemical formula search for easier usage and better performance. Besides simple chemical formula search, finding isotopes, polymers, multicomponent and non-stoichiometric formulas is also available in JChem Base. The formula search method uses JChem Base's cd_formula column which contains the string formula of the molecule, but it is also possible to use any other custom user column that contain valid chemical formulas.
The supported chemical formula features are described below.
In case of ambiguous symbols please use the appropriate chemical symbol of the element. Upper case letter defines that a new chemical element is starting. Spaces are ignored between different chemical symbols and numbers both in the query and in the target formula. E.g.: Al2O3 = Al 2 O 3 = Al2 O3
It is useful to separate ambiguous atom symbols with spaces, e.g.: silicon = Si ≠ S I, NaLi = Na Li ≠ N Al I = NAlI.
Accepted forms are e.g.: C7H14O ; c7h14o ; c7H14o ; Si or si for silicon; SI or sI for sulfur and iodine.
Any order of atoms is accepted, e.g. C7H14O , H14C7O , OC7H14 . A chemical symbol can appear in the formula multiple times, e.g.: CH3COOH = C2H4O2 , both are accepted.
Both open and closed intervals are interpreted to set minimum and/or maximum number of type of atoms and groups.
As a formula e.g.: C-7 H10-14 O0- signifies molecules with maximum 7 carbon atoms, minimum 10 and maximum 14 hydrogen atoms and any number of oxygen atoms both on query and target side.
Query form e.g.: (CH2)5-7 O0- N-3 signifies molecules with carbon atoms between 5 and 7, hydrogen atoms between 10 and 14, any number of oxygen atom and maximum 3 nitrogen atoms.
The components should be separated with a period ( . ) in multicomponent search. The sequence of the components is not important. The coefficient of each component can be set by the appropriate numbers, fractions or intervals. As a special index 'x' signs any number of the indicated component in this formula. An omitted coefficient defaults to 1.
Accepted forms are e.g: 5C4H6.Na , 3/4 Na . 2-5 C4H6 , xCuCl2.xH2O means any number of CuCl2 with any number of H2O . (C2H4O.C8H9)n defines a copolymer with C_{2}H_{4}O and C_{8}H_{9} repeating units.
Isotope search is available using square brackets in the search formula. Accepted form is [mass number followed by chemical symbol], e.g.: C7H12 [2H][3H] O
Trivial abbreviations ([2H] = D; [3H] = T) are also accepted without square brackets! Example: C7H12 DT O
See more examples of acceptable formulas in JChem Base.
To fulfil every requirement, three search types are available to find molecules by chemical formula: Exact , Exact subformula and Subformula search.
Exact search
Exact subformula search
Subformula search
Table 1. Search type results comparison
Query Formula | C7 H14 O | |||
Result | Yes | No | ||
Exact | C7H14O | C7H14O | C6H14O | C7H14OS |
Exact Subformula | C7H14OS | C7H14OSi | C6H14O | C7H16OSi |
Subformula | C7H16OSi | C8H14O2S | C6H14O | C7H14S |
Table 2. Query formula can match polymer in Subformula search
Query Formula | C4 H6 O2 | ||
Search type | Exact | Exact subformula | Subformula |
Target formula | (C4H8O4)n | (C4H8O4)n | (C4H8O4)n |
Find | No | No | Yes |
Here you can find some examples on accepted query formulas in JChemBase.
Spaces can divide the formula at any logical point. | Even mixed upper case and lower case letters are accepted for chemical symbols. | Any order of the elements is accepted. | The groups in parentheses are multiplied. | Any element can be excluded by zero. | |
C9H21O5PSi
| C9H21O5PSi | c9h21o5psi | C9 O5 H21 Si P | (CH3)3 (CH2)6 O5 Si P | C9 O5 H21 Si P N0 |
C9 H21 O5 P Si | c9 H21 O5 p Si | Si P O5 H21 C9 | (CH2)9 H3 O5 Si P | Si P O5 H21 C9 S0 | |
C 9 H 21 O 5 P Si | c 9 h 21 o 5 p si | H21 Si O5 P C9 | (CH4O)5 C4 H Si P | H21 Si O5 P C9 Cl0 |
works as a mathematical logic | defines polymer molecule | specifies combined groups |
(CH3)3 Si C3H5 | (C8H8)n | (F+Cl+Br+I)1 Sum of F, Cl, Br and I is equal to 1, i.e. there is only 1 halogen atom in the molecule. |
C3H9 Si C3H5 | (C8H8)L | (Cl+Br+I) Sum of Cl, Br and I is equal to 5 in a molecule . |
C6H14 Si | polystyrene | (F+Cl+Br+I)0 No halogens are allowed in the molecule. |
Open intervals
Closed intervals
For example: (CH2)5-7 O0- N-3 signifies molecules with carbon atoms between 5 and 7, hydrogen atoms between 10 and 14, any number of oxygen atom and maximum 3 nitrogen atoms.
Query formula | Results in Exact formula search |
(CH2)5-7 O0- N-3 | C5H10N3 |
C5H11N3 | |
C5H12N3 | |
C5H13N3 | |
C5H14N3 | |
C6H10N3 | |
C6H11N3 | |
C6H12N3 | |
C6H13N3, ... |