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

C6H5BrClN

Molecular formula

Molar mass206.47g/mol
Monoisotopic mass204.9294Da
Nominal mass205Da
Rings plus double bonds
4
Details
Monoisotopic mass
204.929389 Da
Average mass, unrounded
206.467000 g/molShown above to 2 decimals, the precision of the least precise standard atomic weight in the formula.
Mass defect
−0.0706 Da
Atoms
14

Isotope pattern

M · C6H5BrClN · most intense peak 206.9271

0255075100205206207208209210211206.9271100%204.929477.2%208.924524.2%207.93026.9%205.93245.34%209.92751.66%%mass (Da)
IonFormulam/z
C6H5BrClN 204.9294
C6H6BrClN+ 205.9367
C6H5BrClNNa+ 227.9186
C6H5BrClKN+ 243.8925
C6H9BrClN2+ 222.9632
C6H7BrClN2+ 103.4720
C6H5BrClN+ 204.9288
C6H4BrClN− 203.9221
C6H5BrCl2N− 239.8988
Peak list
Mass (Da)Relative intensityAbundance
204.9293977.23 %35.8506 %
205.932435.34 %2.4781 %
206.92713100.00 %46.4181 %
207.930176.90 %3.2047 %
208.9244624.24 %11.2526 %
209.927451.66 %0.7728 %
210.930420.049 %0.0227 %

Elemental composition

ElementAtomsMass (g/mol)Mass %
C Carbon672.06634.90
H Hydrogen55.0402.44
Br Bromine179.90438.70
Cl Chlorine135.45017.17
N Nitrogen114.0076.78

Elemental analysis

ElementCalcd (%)Found (%)Δ
C34.90——
H2.44——
N6.78——
Anal. Calcd for C6H5BrClN: C, 34.90; H, 2.44; N, 6.78.
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.