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1. Introduction

qmol is a simple chemical calculator, which calculates molecular weights and elemental composition of compounds given their chemical formula.

1.1 Calculator Features

qmol is designed to be able to parse any chemical formula that can be unambiguously interpreted if written as a simple character sequence (i.e., without subscript and superscript formating). If you can understand a chemical formula, chances are qmol will understand it in exactly the same way.

qmol can deal with:

• Unlimited number of nested subgroups: (CH3(C6H3)N(SiMe(CMe3)2))2Y(thf)2(CH(SiMe3)2). (915.484 g/mol, with thf defined as C4H9)
• Multicomponent compounds: K2SO4+Al2(SO4)3+24H2O.
• Subtraction of formulas: 2CH3CH2OH-H2O will give the MW of diethyl ether.
• Fractional coefficients: Cu3.14O2.72.
• One letter amino acid symbols evaluated in square brackets: [APCH].
• User-defined symbols.

qmol has a built-in definition editor, which is used to define new group symbols. Additionally, I added pre-defined sets of useful groups, namely amino acids and alkyls/aryls.

Even though qmol is designed to be used with a graphical interface, you can also start it from the command line with a chemical formulae as a arguments (you may need to put in in quotes so that the shell doesn't try to interpret it). It will printout the molecular weight and composition (according to a format you can specify in the GUI), and exit.

At this point qmol doesn't perform any estimate of the errors involved in the calculations. You are expected to understand that molecular weight and elemental composition data can only be as accurate as the constituent element weights are.

I added a history feature so you can track the formulae you have already entered, their sum formula and their weight.

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