Methyl isothiocyanate Lewis Structure

Methyl isothiocyanate Lewis Structure: C₂H₃NS Lewis Structure, tetrahedral Geometry, sp3 Hybridization & Polarity

Methyl isothiocyanate Key Facts

The Methyl isothiocyanate Lewis structure is C–N single bond and 3 C–H single bond; the central C has 4 electron domains (0 lone pairs), giving a tetrahedral electron-domain arrangement and a tetrahedral molecular geometry with a 109.5° bond angle. C is best described as sp3-hybridized, and Methyl isothiocyanate is polar because the tetrahedral shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Methyl isothiocyanate (C₂H₃NS)

Chemical Formula	C₂H₃NS
CAS Number	556-61-6
Total Valence Electrons	22
Lewis Structure	C–N single bond and 3 C–H single bond
Electron-Domain Geometry	tetrahedral
Molecular Geometry	tetrahedral
Hybridization Model	sp3 (central C)
Bond Angle	109.5°
Polarity	Polar molecule

PubChem (CID 11167) and NIST list Methyl isothiocyanate as C ₂H ₃NS with CAS 556-61-6; molecular weight ≈ 73.12 g/mol. View CAS 556-61-6 dictionary details on Guidechem →

Applications of Methyl isothiocyanate (CAS 556-61-6)

This organic compound is used as a solvent, intermediate or specialty reagent in fine-chemical, pharmaceutical and materials synthesis; specify grade and impurity profile when sourcing.

Solvent / Reagent Medium for reactions, extraction or formulation.

Intermediate Building block for downstream derivatives.

Specialty Use Targeted role in pharma/fragrance/materials.

Procurement Note "Methyl isothiocyanate" is supplied in multiple commercial grades and package sizes. Specify purity, grade, moisture/impurity limits, package (cylinder, drum or bulk) and intended process, and use CAS 556-61-6 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Methyl isothiocyanate Lewis structure we first count the total valence electrons. C₂H₃NS contains 2×4 (C) + 3×1 (H) + 5 (N) + 6 (S); the net charge of 0 gives a total of 22 valence electrons to place.

The central atom is C. It is the least electronegative atom capable of forming multiple bonds and is surrounded by the more electronegative terminal atom(s); hydrogen, when present, always occupies a terminal position. Electronegativity considerations place the electron density toward the terminal atom(s).

Valence-electron count

Total valence electrons = 2×4 (C) + 3×1 (H) + 5 (N) + 6 (S) = 22 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place C at the center and connect each surrounding atom with a single bond, complete octets on the terminal atoms, and place any remaining electrons on the central atom. The resulting electron distribution is: C–N single bond and 3 C–H single bond; no lone pairs on C.

Counting bonding and nonbonding electrons around C therefore satisfies the octet/expanded-octet requirement for the drawn structure.

C–N C–H ×3

C: 0 lone pairs, 4 bonding domains

4 bonding domains + 0 lone pairs = 4 electron domains

Octet Rule: Why C Has Eight Electrons C forms 4 bond(s) and retains 0 nonbonding electron(s), reaching an octet. No expanded octet is required for this second-row (or octet-satisfying) central atom.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 4 electron domains around C arrange to minimize mutual repulsion, giving an tetrahedral electron-domain geometry.

Because 0 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is tetrahedral; the C bond angle is set to 109.5° rather than the ideal value for the electron-domain geometry.

Repulsion hierarchy

A useful VSEPR approximation is: lone pair–lone pair repulsion > lone pair–bonding pair repulsion > bonding pair–bonding pair repulsion. With 0 lone pair(s) on C, the lone-pair domains occupy positions that minimize overall repulsion while pushing the bonding domains (and therefore the bonded atoms) closer together.

Hybridization & Formal Charge

In the conventional localized-bond model, C uses sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (4 bonding + 0 lone pair).

Formal-charge check

Formal charge on central C = V − N − ½B = 4 − 0 − ½×8 = 3. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp3 is a compact model for the 4 electron-domain directions around C; full quantum-chemical treatments use molecular orbitals.

Is Methyl isothiocyanate Polar or Nonpolar?

Methyl isothiocyanate is polar. The tetrahedral shape prevents cancellation of the bond dipoles. The bond dipoles do not cancel, leaving a net molecular dipole, which strongly influences solvation behavior and intermolecular interactions.

Expert Quote — Structural Chemistry Perspective

The decisive structural fact is not simply that the individual bonds are polar; it is whether molecular symmetry allows their vector sum to vanish. In Methyl isothiocyanate the tetrahedral arrangement prevents cancellation, so a permanent dipole remains.

Interpretation consistent with standard VSEPR / molecular-geometry references.

This polarity profile underpins its behavior as a solvent, reactant or process intermediate; when sourcing, specify grade and container compatibility.

Structural Comparison Table

Species	Formula	Central Atom	Electron Domains	Molecular Geometry	Polarity
Methyl isothiocyanate	C₂H₃NS	C	4	tetrahedral	Polar
Carbon dioxide	CO₂	C	2	linear	Nonpolar
Carbon monoxide	CO	C	2	linear (diatomic)	Polar
Carbon disulfide	CS₂	C	2	linear	Nonpolar
Methane	CH₄	C	4	tetrahedral	Nonpolar
Ethane	C₂H₆	C	4	tetrahedral	Nonpolar

Practice question Starting from the 22 valence electrons of C₂H₃NS, draw the Lewis structure and confirm the central C atom is sp3-hybridized with tetrahedral geometry. What happens to the bond angle if one terminal atom is replaced by a more electronegative substituent?

Looking for industrial bulk or specified-grade supplies of Methyl isothiocyanate (CAS 556-61-6)? Browse Supplier on Guidechem →

FAQs

Is C₂H₃NS polar or nonpolar?

Methyl isothiocyanate is polar. Its tetrahedral geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Methyl isothiocyanate?

C–N single bond and 3 C–H single bond; no lone pairs on C. It uses all 22 valence electrons and the preferred structure carries a formal charge of 3 on the central atom.

What is the bond angle in Methyl isothiocyanate?

The C angle is about 109.5°. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.

What is the hybridization of C in Methyl isothiocyanate?

The conventional model is sp3. Methyl isothiocyanate has 4 electron domains around the central C.

What is the CAS number of Methyl isothiocyanate?

The CAS number is 556-61-6. PubChem (CID 11167) and NIST identify this with C₂H₃NS; use it to locate suppliers and database records.

References

PubChem CID 11167, Methyl isothiocyanate. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Methyl isothiocyanate. Formula, CAS Registry Number and thermochemical / spectroscopic data.
IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for Methyl isothiocyanate (CAS 556-61-6).

Technical scope: Lewis structures, VSEPR and hybridization are model-based descriptions for chemical communication and structure prediction; actual molecular electronic structure is more accurately represented by molecular-orbital and quantum-chemical methods. Commercial grades vary substantially by supplier and intended use; CAS 556-61-6 identifies the substance, not a universal purity specification.

Make Guideview Preferred Source on Google

Methyl isothiocyanate Lewis Structure