Molar mass

Molar mass, exact mass and elemental composition for any formula, compound or SMILES, with the isotope pattern, HRMS adducts and an elemental analysis check.

Formula or compound

Read as a formula
Examples:

Hydrates with · or *, charges as Fe3+ or SO4{2-}, labelled atoms as [13C] or D.

Molar mass

C13H30ClN3

Molecular formula

Molar mass263.85g/mol
Monoisotopic mass263.2128Da
Nominal mass263Da
Rings plus double bonds
0
Details
Monoisotopic mass
263.212826 Da
Average mass, unrounded
263.854000 g/molShown above to 2 decimals, the precision of the least precise standard atomic weight in the formula.
Mass defect
0.2128 Da
Atoms
47

Isotope pattern

M · C13H30ClN3 · most intense peak 263.2128

0255075100263.0263.5264.0264.5265.0265.5266.0266.5267.0267.5268.0268.5263.2128100%265.210233.1%264.215815.5%266.21295.01%%mass (Da)
IonFormulam/z
C13H30ClN3 263.2128
C13H31ClN3+ 264.2201
C13H30ClN3Na+ 286.2020
C13H30ClKN3+ 302.1760
C13H34ClN4+ 281.2467
C13H32ClN32+ 132.6137
C13H30ClN3+ 263.2123
C13H29ClN3− 262.2055
C13H30Cl2N3− 298.1822
Peak list
Mass (Da)Relative intensityAbundance
263.21283100.00 %64.9314 %
264.2158015.50 %10.0653 %
265.2101833.12 %21.5047 %
266.212945.01 %3.2533 %
267.215830.361 %0.2344 %
268.218720.016 %0.0105 %

Elemental composition

ElementAtomsMass (g/mol)Mass %
C Carbon13156.14359.18
H Hydrogen3030.24011.46
Cl Chlorine135.45013.44
N Nitrogen342.02115.93

Elemental analysis

ElementCalcd (%)Found (%)Δ
C59.18——
H11.46——
N15.93——
Anal. Calcd for C13H30ClN3: C, 59.18; H, 11.46; N, 15.93.
How the masses are calculated

The molar mass sums the IUPAC standard atomic weights, using the conventional value for elements whose weight is given as an interval (hydrogen 1.008, carbon 12.011, sulfur 32.06). It is shown to the number of decimals of the least precise atomic weight in the formula, so CuSO4·5H2O gets two decimals because of sulfur; the unrounded value is under Details.

The monoisotopic mass uses the mass of the most abundant isotope of every element, the nominal mass its mass number. Labelled atoms, written [13C], D or T, count with their own nuclide mass and are taken as fully enriched. For an ion, one electron mass, 0.000 548 579 909 u, is subtracted per positive charge and added per negative charge.

How the isotope pattern is computed

Every element's natural isotope distribution is raised to its atom count by repeated squaring, and the element distributions are then convolved with each other. In centroid mode the isotopologues are grouped by nominal mass and each group is reported at its intensity-weighted mean m/z, which is what a mass spectrometer at ordinary resolution shows; this is exact apart from dropping contributions below 10−12 of the largest. Fine structure keeps isotopologues apart, merges those closer than 0.1 mDa and drops those below 10−8 of the largest, which resolves, for example, 34S from 13C2.

Adduct m/z values follow m/z = (M + adduct − z·me) / |z|. The copy button gives the line in the form the ACS journals print, for example “[M + H]+ Calcd for C8H11N4O2 195.0877”. The ACS guidelines ask that found and calculated m/z agree within 0.003 m/z units, the limit the found m/z check uses.

Elemental analysis

Calculated percentages are mass fractions from the standard atomic weights. Journals ask for found values within ±0.4 % (absolute) of the calculated ones. If a sample holds solvent, enter it as a solvate, for example 0.5 × H2O, and the calculated values are for C8H10N4O2·0.5H2O.

Sources

Standard atomic weights: IUPAC Commission on Isotopic Abundances and Atomic Weights, “Standard atomic weights of the elements 2021”, Pure Appl. Chem. 94, 573 (2022). Isotope masses and natural abundances: NIST, Atomic Weights and Isotopic Compositions for All Elements (Standard Reference Database 144). Electron mass: CODATA 2018, Rev. Mod. Phys. 93, 025010 (2021). Reporting criteria: ACS Author Guidelines for The Journal of Organic Chemistry and Organic Letters.