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To determine whether Isocyanic acid / Cyanic acid (CHNO) is polar or nonpolar, the decisive question is whether the bond dipoles of the molecule cancel once its three-dimensional shape is taken into account. Isocyanic acid / Cyanic acid is an isocyanate, built from isocyanate (–N=C=O). As set out in the CHNO Lewis Structure Guide, CHNO has 3 heavy atoms.
The bond polarities follow from electronegativity. The largest differences in the structure are C–O (ΔEN ≈ 0.89) and C–N (ΔEN ≈ 0.49), so electron density is pulled toward oxygen. In three dimensions, the nitrogen centre is bent; the remaining non-bonding pair closes the angle to roughly 120°. As a result, the calibrated dipole moment is μ ≈ 1.77 D. Treated as a dilute ideal gas at 298 K and 1 atm, the Debye equation converts that dipole into a relative permittivity of about 1.01173 — a number very close to unity, which is exactly what a gas-phase value should look like.
For formulation and process work, the useful consequences are these: the calculated topological polar surface area is 40.9 Ų, 1 hydrogen-bond donor and 2 hydrogen-bond acceptors, the Crippen calculated partition coefficient is logP ≈ -0.10 and the calculated molar refractivity is 8.41 cm³ mol⁻¹. A negative logP indicates a net preference for the aqueous phase over octanol, which is what one expects when polar and ionisable groups dominate a small molecule. PubChem’s curated experimental record adds: Isocyanic acid / Cyanic acid is 996 [mm Hg] @25 °C.
Isocyanic acid / Cyanic acid (CAS 75-13-8 / 420-05-3) is an isocyanate, supplied as an industrial chemical. Its polarity matters for the same reason it matters for any substance of this class: it decides which phases the material will enter, how strongly it adsorbs onto polar surfaces, and how much energy a separation will cost.
The measured physical behaviour recorded for this substance is consistent with that picture. Vapor Pressure: 996 [mm Hg] @25 °C. These are database values and should be read with the conditions (temperature, purity, pressure) that the source states.
Treated as a dilute gas, the calculated relative permittivity is about 1.01173 at 298 K and 1 atm. That figure is close to unity because a gas is mostly empty space: it is a useful consistency check on the dipole, but it is not the number to use when sizing a liquid process, where condensed-phase permittivity and specific interactions dominate.
Structurally the reactivity sits in isocyanate (–N=C=O). That functional inventory, together with the substantial dipole, is what predicts the solubility and adsorption behaviour: polar groups give the molecule a handle on polar solvents and on polar surfaces, while the hydrocarbon portion resists them.
PubChem’s GHS record for this substance lists H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral] and H312 (100%): Harmful in contact with skin [Warning Acute toxicity, dermal]. Those classifications, not the polarity of the molecule, normally determine packaging, labelling, ventilation and transport requirements.
In short, specify Isocyanic acid / Cyanic acid by assay, water content, impurity profile, packaging and transport class, and state the intended application on the enquiry. The polarity analysis above explains behaviour in use; it does not replace a specification.
The comparison below places CHNO next to structurally related substances from the same catalogue. Dipole moments come from one consistent protocol (GFN2-xTB//MMFF94, gas phase, single conformer) and are quoted only where that protocol has been validated; where it has not, the cell says so instead of giving a number. Permittivities are dilute-gas estimates from the Debye equation, logP values are Crippen calculations, and the solubility column is a qualitative inference from the calculated descriptors rather than a measurement.
| Compound | Dipole Moment | Approx. Gas εr | log P / XlogP | Water Solubility Behavior | Industrial Sourcing |
|---|---|---|---|---|---|
| CHNO | ≈1.77 D (calc.) | ≈1.0117 | logP ≈ -0.10 | 996 [mm Hg] @25 °C | See supply listing |
| C2H3NO | ≈1.98 D (calc.) | ≈1.0152 | logP ≈ -0.05 | Moderate to high (inferred from logP < 0) | See supply listing |
| CClNO | ≈0.79 D (calc.) | ≈1.0039 | logP ≈ 0.48 | Moderate (inferred from logP) | See supply listing |
| CH3NO | ≈3.74 D (calc.) | ≈1.0489 | logP ≈ -0.90 | Moderate to high (inferred from logP < 0) | See supply listing |
| CNO | not applicable (ion) | — | logP ≈ -0.11 | Dissolves by dissociation; ionic hydration dominates | See supply listing |
The spread across this table is the point: composition alone does not set the polarity verdict. CHNO sits where it does because of the balance between its polar functional groups and the asymmetry of its shape, and any of the neighbouring entries can be the better choice once the temperature, the phase and the required polarity window are fixed.
“A dipole of about 1.77 D puts CHNO in the substantial range, and it comes directly from the geometry: the nitrogen centre is bent; the remaining non-bonding pair closes the angle to roughly 120°. A calculated logP of -0.10 tells you where it will partition. The curated experimental record is consistent: 996 [mm Hg] @25 °C.”
Regulatory status is specific to the substance and to the jurisdiction, and it changes. For CAS 75-13-8 / 420-05-3 the authoritative public sources are the ECHA registered-substance database for the EU, and the OSHA and NIOSH tables for occupational exposure in the United States.
PubChem’s GHS record for this substance lists H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral] and H312 (100%): Harmful in contact with skin [Warning Acute toxicity, dermal]. These statements are the ones that must appear on the label and in section 2 of the safety data sheet; they, rather than the polarity of the molecule, drive classification, packaging group and transport documentation.
No occupational exposure limit for this substance is quoted in this article, because none was present in the database record used here. Publishing a limit that is not on the record would be worse than publishing none: obtain the applicable value from the OSHA Z-table, the NIOSH pocket guide or the equivalent national instrument before designing the ventilation or monitoring programme.
From a compliance and sustainability standpoint, the polarity of CHNO is a means rather than an end. It determines which solvent can replace another, how completely the substance can be recovered from a stream, and how much energy the separation will cost — so it belongs in the process justification, while the hazard classification and the exposure limits belong in the safety case.
A purchase enquiry for Isocyanic acid / Cyanic acid (CAS 75-13-8 / 420-05-3) should state the grade, assay basis, permitted impurity limits, water content, packaging, and the transport and regulatory status required for the destination market. Where the substance is used as a reagent or intermediate, the impurity profile usually matters more than the nominal percentage.
Because polarity governs phase behaviour, it also governs recovery: a substantial molecule is easier to strip from a non-polar stream and harder to dry than a non-polar one, and vice versa. Confirm the Guidechem supply listing for current availability and compare lots on the certificate of analysis rather than on the label alone.
Looking for commercial bulk supplies or technical documentation for Isocyanic acid / Cyanic acid (CAS 75-13-8 / 420-05-3)?
Isocyanic acid / Cyanic acid is polar. The bond dipoles do not cancel, giving a calculated dipole of about 1.77 D.
The calculated gas-phase dipole is approximately 1.77 D, obtained as a GFN2-xTB single point on an MMFF94-optimised geometry and then calibrated. Against 60 molecules with published gas-phase dipoles the calibrated protocol has a median residual of about 0.12 D and a 90th percentile near 0.3 D; it returns exactly zero whenever symmetry requires zero.
The nitrogen centre is bent; the remaining non-bonding pair closes the angle to roughly 120°. The vector sum of the bond dipoles is what remains once the shape is fixed, so geometry — not the mere presence of polar bonds — is the deciding factor.
The dilute-gas estimate from the Debye equation at 298 K and 1 atm is about 1.01173. That is a gas-phase number and is close to unity by construction; it is not a liquid dielectric constant, and no liquid value is quoted here unless it appears in the cited database record.
Not in routine tabulations. Snyder P′ was developed for conventional liquid chromatographic solvents, and this substance is outside the scope of that scale. Dipole moment, calculated logP and hydrogen-bond counts are the descriptors used here instead.
The curated database record states: 996 [mm Hg] @25 °C. The calculated logP of -0.10 is consistent with that behaviour.
Grade, assay basis, water content, the declared impurity profile, packaging and the transport classification, plus the regulatory status required for the destination market. PubChem’s GHS record for this substance lists H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral] and H312 (100%): Harmful in contact with skin [Warning Acute toxicity, dermal].
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