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

C6H10Na3O10P

Molecular formula

Molar mass342.079g/mol
Monoisotopic mass341.9705Da
Nominal mass342Da
Details
Monoisotopic mass
341.970466 Da
Average mass, unrounded
342.079070 g/molShown above to 3 decimals, the precision of the least precise standard atomic weight in the formula.
Mass defect
−0.0295 Da
Atoms
30

Isotope pattern

M · C6H10Na3O10P · most intense peak 341.9705

0255075100341.5342.0342.5343.0343.5344.0344.5345.0345.5346.0346.5341.9705100%342.97396.99%343.97502.26%%mass (Da)
IonFormulam/z
C6H10Na3O10P 341.9705
C6H11Na3O10P+ 342.9777
C6H10Na4O10P+ 364.9597
C6H10KNa3O10P+ 380.9336
C6H14NNa3O10P+ 360.0043
C6H12Na3O10P2+ 171.9925
C6H10Na3O10P+ 341.9699
C6H9Na3O10P− 340.9632
C6H10ClNa3O10P− 376.9399
Peak list
Mass (Da)Relative intensityAbundance
341.97047100.00 %91.3908 %
342.973926.99 %6.3840 %
343.974962.26 %2.0689 %
344.978220.146 %0.1337 %
345.979450.023 %0.0213 %

Elemental composition

ElementAtomsMass (g/mol)Mass %
C Carbon672.06621.07
H Hydrogen1010.0802.95
Na Sodium368.96920.16
O Oxygen10159.99046.77
P Phosphorus130.9749.05

Elemental analysis

ElementCalcd (%)Found (%)Δ
C21.07——
H2.95——
Anal. Calcd for C6H10Na3O10P: C, 21.07; H, 2.95.
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.