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

CO3Tl2

Molecular formula

Molar mass468.77g/mol
Monoisotopic mass469.9336Da
Nominal mass470Da
Details
Monoisotopic mass
469.933599 Da
Average mass, unrounded
468.768000 g/molShown above to 2 decimals, the precision of the least precise standard atomic weight in the formula.
Mass defect
−0.0664 Da
Atoms
6

Isotope pattern

M · CO3Tl2 · most intense peak 469.9336

0255075100466467468469470471472469.9336100%467.931583.4%465.929417.5%470.93701.2%%mass (Da)
IonFormulam/z
CO3Tl2 469.9336
CHO3Tl2+ 470.9409
CNaO3Tl2+ 492.9228
CKO3Tl2+ 508.8968
CH4NO3Tl2+ 487.9674
CH2O3Tl22+ 235.9741
CO3Tl2+ 469.9331
CClO3Tl2− 504.9030
Peak list
Mass (Da)Relative intensityAbundance
465.9294317.45 %8.5584 %
466.932870.209 %0.1023 %
467.9315283.44 %40.9196 %
468.934960.998 %0.4893 %
469.93361100.00 %49.0380 %
470.937051.20 %0.5863 %
471.937860.616 %0.3019 %

Elemental composition

ElementAtomsMass (g/mol)Mass %
C Carbon112.0112.56
O Oxygen347.99710.24
Tl Thallium2408.76087.20

Elemental analysis

ElementCalcd (%)Found (%)Δ
C2.56——
Anal. Calcd for CO3Tl2: C, 2.56.
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.