Generating one or more molecular formulae from a mass and error (a maximum error of 0.05 Da is allowed) generates all possible formulae depending on the elemental option settings and then ranks these formulae based on the number of matching hits in the database. no multi component mixtures, no compounds with solvents of hydration, etc.) Pre-selection of the isotope filter removes all isotopically labeled compounds from the search results. Selection of the single component or ignore isotopes filters means that only chemicals containing one component will be returned (i.e. An example search such as 228.1 +/- 5 ppm gives 215 results in a Table or Tile format. The search can be performed ignoring multicomponent structures and ignoring isotopes. A search can be performed on a single mass +/- error, either in Da or ppm. This search will be of particular value for screening and non-targeted analysis users. An example of the difference is the empirical formula for glucose, which is CH2O, while its molecular formula requires all numbers to be increased by a factor of six, giving C6H12O6.This search is primarily incorporated to allow a user to search the database for chemicals matching a particular monoisotopic mass.

Molecular formulas indicate the simple numbers of each type of atom in a molecule of a molecular substance, and are thus sometimes the same as empirical formulas, and at other times require larger numbers than do empirical formulas. The simplest types of chemical formulas are called empirical formulas, which use only letters and numbers indicating atomic proportional ratios. Chemical formulas are more limiting than chemical names and stuctural formulas. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. A chemical formula is not a chemical name, and it contains no words. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. Freebase (4.50 / 2 votes) Rate this definition:Ī chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, and plus and minus signs.

Chemical formula search