Nitrogen Rule Parity

Check nitrogen-rule parity for an even-electron molecular ion.

Description

Nitrogen-rule parity screening compares nominal-mass parity with nitrogen-count parity.

Nitrogen-rule parity screening compares nominal-mass parity with nitrogen-count parity. This tool implements a same-parity rule that must be matched to the species being considered.^{[1, 2]}

Compare nominal-mass and nitrogen-count parity using the implemented same-parity rule. Establish the appropriate species and ion convention separately.

When to use Nitrogen Rule Parity

Use this tool to compare nominal-mass and nitrogen-count parity using the implemented same-parity rule. Establish the appropriate species and ion convention separately.

Prepare the measured profile, formula counts, upstream model outputs or caller-defined reference criteria requested. Keep paired entries aligned and units, sample basis and preprocessing consistent.

How to use Nitrogen Rule Parity and understand its results

Prepare the measured profile, formula counts, upstream model outputs or caller-defined reference criteria requested. Keep paired entries aligned and units, sample basis and preprocessing consistent.
Enter nominalMass, nitrogenAtoms using the field table and calculation rules, then run the tool.
Read oddMass, oddNitrogen, consistent. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
nominalMass	Nominal mass	number	Required
nitrogenAtoms	Nitrogen atoms	number	Required

Enter nonnegative safe integers. Return odd-mass and odd-nitrogen flags and their equality.

consistent=(nominalMass mod2)=(nitrogenCount mod2)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
oddMass	Odd mass	boolean
oddNitrogen	Odd nitrogen	boolean
consistent	Consistent	boolean

json

{
  "input": {
    "nominalMass": 137,
    "nitrogenAtoms": 1
  },
  "output": {
    "oddMass": true,
    "oddNitrogen": true,
    "consistent": true
  }
}

Limitations and assumptions

The tool does not distinguish neutral molecules, radical ions, even-electron ions or adducts. Ion type can change the appropriate parity rule; a true flag is not proof of a valid formula.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Double Bond Equivalent: Calculate molecular double-bond equivalents from C/H/N/halogen counts. For a complementary task, use Monoisotopic Formula Mass: Sum neutral monoisotopic mass from C/H/N/O/S/P atomic compositions.

Further background: Protocol for Structure Determination of Unknowns by EI Mass Spectrometry.

References

Nitrogen Rule Parity — tool.io
Protocol for Structure Determination of Unknowns by EI Mass Spectrometry — National Institute of Standards and Technology

Similar or alternative tools

Double Bond Equivalent
Calculate molecular double-bond equivalents from C/H/N/halogen counts.
Monoisotopic Formula Mass
Sum neutral monoisotopic mass from C/H/N/O/S/P atomic compositions.