Acrolein Lewis Structure

Acrolein Lewis Structure: C₃H₄O Lewis Structure, trigonal planar Geometry, sp2 Hybridization & Polarity

Acrolein Key Facts

The Acrolein Lewis structure is C–C double bond and 2 C–H single bond; the central C has 3 electron domains (0 lone pairs), giving a trigonal planar electron-domain arrangement and a trigonal planar molecular geometry with a 120° bond angle. C is best described as sp2-hybridized, and Acrolein is polar because the trigonal planar shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Acrolein (C₃H₄O)

Chemical Formula	C₃H₄O
CAS Number	107-02-8
Total Valence Electrons	22
Lewis Structure	C–C double bond and 2 C–H single bond
Electron-Domain Geometry	trigonal planar
Molecular Geometry	trigonal planar
Hybridization Model	sp2 (central C)
Bond Angle	120°
Polarity	Polar molecule

PubChem (CID 7847) and NIST list Acrolein as C ₃H ₄O with CAS 107-02-8; molecular weight ≈ 56.06 g/mol. View CAS 107-02-8 dictionary details on Guidechem →

Applications of Acrolein (CAS 107-02-8)

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 "Acrolein" 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 107-02-8 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Acrolein Lewis structure we first count the total valence electrons. C₃H₄O contains 3×4 (C) + 4×1 (H) + 6 (O); 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 = 3×4 (C) + 4×1 (H) + 6 (O) = 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–C double bond and 2 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=C C–H ×2

C: 0 lone pairs, 3 bonding domains

3 bonding domains + 0 lone pairs = 3 electron domains

Octet Rule: Why C Has Eight Electrons C forms 3 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 3 electron domains around C arrange to minimize mutual repulsion, giving an trigonal planar 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 trigonal planar; the C bond angle is set to 120° 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 sp2 hybrid orbitals to form the 3 equivalent electron-domain directions (3 bonding + 0 lone pair).

Formal-charge check

Formal charge on central C = V − N − ½B = 4 − 0 − ½×8 = 2. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp2 is a compact model for the 3 electron-domain directions around C; full quantum-chemical treatments use molecular orbitals.

Is Acrolein Polar or Nonpolar?

Acrolein is polar. The trigonal planar 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 Acrolein the trigonal planar 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
Acrolein	C₃H₄O	C	3	trigonal planar	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 C₃H₄O, draw the Lewis structure and confirm the central C atom is sp2-hybridized with trigonal planar 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 Acrolein (CAS 107-02-8)? Browse Supplier on Guidechem →

FAQs

Is C₃H₄O polar or nonpolar?

Acrolein is polar. Its trigonal planar geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Acrolein?

C–C double bond and 2 C–H single bond; no lone pairs on C. It uses all 22 valence electrons and the preferred structure carries a formal charge of 2 on the central atom.

What is the bond angle in Acrolein?

The C angle is about 120°. Lone-pair repulsion compresses the angle from the ideal trigonal planar value.

What is the hybridization of C in Acrolein?

The conventional model is sp2. Acrolein has 3 electron domains around the central C.

What is the CAS number of Acrolein?

The CAS number is 107-02-8. PubChem (CID 7847) and NIST identify this with C₃H₄O; use it to locate suppliers and database records.

References

PubChem CID 7847, Acrolein. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Acrolein. 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 Acrolein (CAS 107-02-8).

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 107-02-8 identifies the substance, not a universal purity specification.

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Acrolein Lewis Structure

Acrolein Lewis Structure