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C2H5OH Lewis structure (ethanol): connectivity, lone pairs, and molecular shape

What is the correct Lewis structure for C2H5OH (ethanol), including connectivity, bonds, and lone pairs?

Subject: General Chemistry Chapter: Chemical Bonds Topic: Lewis Structure of Polyatomic Molecules with Central Element ( S ) Answer included
c2h5oh lewis structure ethanol Lewis structure CH3CH2OH Lewis diagram ethanol structural formula ethanol valence electrons lone pairs on oxygen formal charge
Accepted answer Answer included

c2h5oh lewis structure refers to the Lewis representation of ethanol, \(\mathrm{C_2H_5OH}\), showing the carbon–carbon–oxygen skeleton, single bonds to hydrogen, and lone pairs on oxygen. The stable structure uses typical valences (C makes 4 bonds, O makes 2 bonds and has 2 lone pairs, H makes 1 bond) with zero formal charges.

Valence-electron count

Ethanol contains 2 carbons, 6 hydrogens, and 1 oxygen. The total number of valence electrons is

\[ 2(4) + 6(1) + 1(6) = 8 + 6 + 6 = 20 \]

These 20 electrons are distributed into bonding pairs (single \(\sigma\) bonds) and nonbonding pairs (lone pairs on oxygen).

Connectivity and bond framework

The accepted connectivity for ethanol is the alcohol framework \(\mathrm{CH_3CH_2OH}\), written as \(\mathrm{H_3C{-}CH_2{-}O{-}H}\). This arrangement places oxygen at the end of the two-carbon chain and assigns the hydroxyl hydrogen directly to oxygen rather than to carbon.

Core structural formula

\(\mathrm{CH_3{-}CH_2{-}O{-}H}\) with all single bonds, and oxygen carrying two lone pairs.

Lone pairs and formal charges

Oxygen in ethanol has two lone pairs. Formal charges verify the neutrality of the preferred Lewis structure.

\[ \mathrm{FC} = V - \left(N + \frac{B}{2}\right) \]

Oxygen has \(V=6\). In \(\mathrm{CH_3CH_2OH}\), oxygen has \(N=4\) nonbonding electrons (two lone pairs) and \(B=4\) bonding electrons (two single bonds: one to carbon and one to hydrogen), giving \(\mathrm{FC_O} = 6 - (4 + 4/2) = 0\). Each carbon has four bonds and no lone pairs, giving formal charge 0. Each hydrogen has one bond, giving formal charge 0.

Local geometry from electron-domain arrangement

Each carbon is surrounded by four electron domains (four \(\sigma\) bonds), giving a tetrahedral electron-domain geometry and approximately \(109.5^\circ\) bond angles in idealized form. Oxygen has four electron domains (two bonds and two lone pairs), giving a tetrahedral electron-domain arrangement but a bent molecular geometry for the \(\mathrm{C{-}O{-}H}\) grouping, with bond angles typically less than \(109.5^\circ\) due to lone-pair repulsion.

Visualization of the Lewis structure of ethanol

Lewis structure of ethanol (C2H5OH): CH3–CH2–O–H with oxygen lone pairs A full Lewis diagram shows the CH3 group bonded to CH2, then to oxygen, then to hydrogen. Oxygen is drawn with two lone pairs. Colored atoms and labeled bonds avoid overlap and show approximate local geometry. Ethanol: CH₃–CH₂–O–H All bonds are single; oxygen carries two lone pairs; formal charges are zero. C CH₃ C CH₂ O H H H H H H lone pair lone pair tetrahedral around C bent around O Condensed formula: CH₃CH₂OH; oxygen has two lone pairs and makes two single bonds.
Lewis structure of ethanol: \(\mathrm{CH_3{-}CH_2{-}O{-}H}\). The oxygen atom has two lone pairs (four nonbonding electrons), and all atoms satisfy typical valence rules with formal charges of zero.

Common structural confusions

  • Hydrogen placement: the \(\mathrm{OH}\) hydrogen is bonded to oxygen, not to carbon.
  • Lone pairs: oxygen has two lone pairs in neutral ethanol; omitting them loses essential electron-count information.
  • Multiple bonds: ethanol contains only single bonds in its standard Lewis description.

Summary statement

\(\mathrm{C_2H_5OH}\) is represented as \(\mathrm{H_3C{-}CH_2{-}O{-}H}\) with two lone pairs on oxygen, giving a neutral Lewis structure consistent with 20 valence electrons and typical tetrahedral electron-domain arrangements around the heavy atoms.

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