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

C6H14O12P2

Molecular formula

Molar mass340.114g/mol
Monoisotopic mass339.9960Da
Nominal mass340Da
Rings plus double bonds
1
Details
Monoisotopic mass
339.996050 Da
Average mass, unrounded
340.113524 g/molShown above to 3 decimals, the precision of the least precise standard atomic weight in the formula.
Mass defect
−0.0040 Da
Atoms
34

Isotope pattern

M · C6H14O12P2 · most intense peak 339.9960

0255075100339.5340.0340.5341.0341.5342.0342.5343.0343.5344.0344.5339.9960100%340.99957.11%342.00052.68%%mass (Da)
IonFormulam/z
C6H14O12P2 339.9960
C6H15O12P2+ 341.0033
C6H14NaO12P2+ 362.9853
C6H14KO12P2+ 378.9592
C6H18NO12P2+ 358.0299
C6H16O12P22+ 171.0053
C6H14O12P2+ 339.9955
C6H13O12P2− 338.9888
C6H14ClO12P2− 374.9655
Peak list
Mass (Da)Relative intensityAbundance
339.99605100.00 %90.9053 %
340.999537.11 %6.4612 %
342.000522.68 %2.4393 %
343.003830.178 %0.1619 %
344.004980.033 %0.0302 %

Elemental composition

ElementAtomsMass (g/mol)Mass %
C Carbon672.06621.19
H Hydrogen1414.1124.15
O Oxygen12191.98856.45
P Phosphorus261.94818.21

Elemental analysis

ElementCalcd (%)Found (%)Δ
C21.19——
H4.15——
Anal. Calcd for C6H14O12P2: C, 21.19; H, 4.15.
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.