Selected theoretical and actual constitutional isomers of molecular formula C₂H₂O₂

Introduction to the constitutional isomers C₂H₂O₂

Percent composition based on atomic masses C= 12.01  H = 1.01  O = 16.00, so  M_r(C₂H₂O₂) = 58.04

Element composition (to two dp): carbon = 41.39%     hydrogen = 3.48%     oxygen = 55.13%

Empirical formula = CHO for molecular formula = C₂H₂O₂

Some of the isomers described may be highly reactive and very thermodynamically unstable e.g. due to weak highly strained bonds, particularly ring compounds, and some may not even exist at all (except theoretically of course!).

They are all functional group isomers of each other.

I can't see any E/Z geometrical isomers or R/S optical isomers.

Not sure on some of the names? Help appreciated?

I've deduced 9 constitutional isomers of C₂H₂O₂ and I think that might be it?

(1) to (4) are open chain aliphatic compounds

 (1, names)  ethynediol, 1,2-dihydoxyethyne, 1,2-dihydroxyacetylene and acetylenediol

An open chain aliphatic compound, alkyne and alcohol functional groups.

Number of low resolution NMR chemical shift δ signal peaks: 1 ¹H and 1 ¹³C (email if disagree?)

 

(2, names)  ethynyl hydroperoxide

An open chain aliphatic compound, alkyne and hydroperoxide functional groups.

Number of low resolution NMR chemical shift δ signal peaks: 2 ¹H and 2 ¹³C (email if disagree?)

¹H NMR ratio of peaks: 1 : 1 (non-equivalent protons)

 

(3, names)  2-hydroxyketene, hydoxyketene

An open chain aliphatic compound with ketene and alcohol functional groups.

tends to tautomerise to glyoxal (4, below)

HO-CH=C=O  CHO-CHO

Number of low resolution NMR chemical shift δ signal peaks: 2 ¹H and 2 ¹³C (email if disagree?)

¹H NMR ratio of peaks: 1 : 1 (for non-equivalent protons)

 

(4, names)  ethane-1,2-dial, oxaldehyde, ethane-1,2-dione and glyoxal

An open chain aliphatic compound, symmetrical, a double aldehyde functional group.

Number of low resolution NMR chemical shift δ signal peaks: 1 ¹H and 1 ¹³C (email if disagree?)

 

(5) to (9) are heterocyclic compounds

(5, names)  hydoxyoxirene, oxirenol

A heterocyclic ring compound, a cyclic ether with an alkene group and also an alcohol functional group.

Number of low resolution NMR chemical shift δ signal peaks: 2 ¹H and 2 ¹³C (email if disagree?)

¹H NMR ratio of peaks: 1 : 1 (for non-equivalent protons)

 

(6, names) oxiranone, oxiran-2-one, acetolactone

A heterocyclic ring compound, highly unstable, very reactive, a cyclic ether and a carbonyl  functional group.

Number of low resolution NMR chemical shift δ signal peaks: 1 ¹H and 2 ¹³C (email if disagree?)

 

(7, names) 1,2-dioxetene

A heterocyclic ring compound, symmetrical, an unsaturated (C=C) cyclic peroxide functional group.

Number of low resolution NMR chemical shift δ signal peaks: 1 ¹H and 1 ¹³C (email if disagree?)

 

(8, names?) based on 1,3-dioxetane?

 A heterocyclic ring compound, symmetrical, a double cyclic ether functional group.

Number of low resolution NMR chemical shift δ signal peaks: 1 ¹H and 1 ¹³C (email if disagree?)

 

(9, names?) methylene group in the 3- position

A heterocyclic ring compound, a cyclic peroxide group and a methylene group as part of an alkene functional group.

Number of low resolution NMR chemical shift δ signal peaks: 1 ¹H and 2 ¹³C (email if disagree?)

Index of sets of isomers for a given molecular formula

Isomerism: introduction, structural isomerism - chain, positional, functional group, tautomerism

Stereoisomerism: introduction, definition, priority rules, E/Z isomerism (cis/trans geometrical isomerism)

Stereoisomerism - R/S isomerism (optical isomerism) - definition - examples explained

Index of all IR, mass, ¹H NMR and ¹³C NMR spectroscopy pages