isomers of C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

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Advanced level organic chemistry PART 14.7: Structural isomers of molecular formula C2H2X4 (X = halogen)

Doc Brown's Advanced Chemistry: Part 14.7: Isomers and extra notes on their properties and uses

The structural isomers of molecular formula C2H2F4 C2H2Cl4 C2H2Br4 and C2H2I4

[Author ©  Dr WP Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK A level chemistry courses, IB advanced chemistry and US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy and analysing the isomers of C2H2X4 [isomerism page updated Feb 9th 2026 *]

* Associated organic chemistry page links

* Index of sets of isomers for a given molecular formula

* This is a big chemistry website, please allow time to explore it

* email doc brown - comments - query? * [privacy policy, cookies and disclaimer]

The two constitutional-structural isomers of molecular formula  C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

Relative molecular mass and percent composition by mass of C2H2X4 based on atomic masses:

C 12.01,  H 1.01, F 19.00,  Cl 35.45,  Br 79.90, I 126.90
Formula of compound Relative molecular mass % carbon % hydrogen % halogen
C2H2F4 102.04 23.54 1.98 74.48
C2H2Cl4 167.84 14.31 1.20 84.49
C2H2Br4 345.64 6.95 0.58 92.47
C2H2I4 533.64 4.50 0.38 95.12

Empirical formula CHX2 for molecular formula C2H2X4

Introduction to isomerism in molecules of formulae C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

If applicable (see isomerism summary at the end of the page)

Structural isomerism  - isomers based on different connectivity's of the constituent atoms, so cannot be spatially identical (but can be defined as having the same shape).

This includes (a) carbon chain variation (usually need a minimum of 4 C atoms), (b) change in position of a substituent (C-X functional group) and (c) functional group isomerism where the atoms have a different connectivity configuration, usually with significant differences in chemical and physical properties.

All the isomerism here is based on the relative positions of the four substituent halogen atoms and no other type of isomerism is possible.

Stereoisomerism - isomers based on the same connectivity of the atoms, but 2D or 3D spatially different, non-superimposable images (e.g. E/Z isomers or mirror image R/S optical isomers)

This is where molecules have the same basic constitutional structural formula, but isomers differ in the 2D/3D arrangement of the atoms. NOT possible for C2H2X4

E/Z stereoisomerism

This was called 'geometrical isomerism' e.g. cis and trans isomers of alkenes or disubstituted cyclic alkanes where there are 3D spatial variations that are not mirror images and not super imposable.

R/S stereoisomerism

This was called 'optical isomerism', the pairs of isomers are called enantiomers which are 3D non-superimposable mirror image forms of the molecule.

The molecule must have a chiral centre (a stereocentre), that is an asymmetric carbon atom with four different atoms/groups attached to it.

Note for the isomers of formulae C2H2F4, C2H2Cl4, C2H2Br4 or C2H2I4

Some of the  C2H2F4, C2H2Cl4, C2H2Br4 or C2H2I4 isomers may be highly reactive and very unstable and some may not even exist at all (except theoretically of course!).

Some of the images of the isomers presented are theoretical, in the sense that some may be so unstable as not to exist, but you will find most, and sometimes all of them, on the internet.

The are 2 constitutional-structural isomers of molecular formula C2H2X4 (X = F, Cl, Br and I), and E/Z or R/S isomerism not possible.

They are all saturated open chain aliphatic compounds derived from halogen tetra-substitution products of alkane hydrocarbon with the formula C2H6 (ethane).

Details of the 2 constitutional structural isomers C2H2F4 C2H2Cl4 C2H2Br4 C2H2I4

isomers of C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4 condensed structural formula skeletal formula constitutional formula

(1) XCH2CX3, 1,1,1,2-tetrafluoroethane, 1,1,1,2-tetrachloroethane, 1,1,1,2-tetrabromoethane, 1,1,1,2-tetraiodoethane condensed constitutional structural formula skeletal formula , where X = F, Cl, Br or I

The abbreviated structural formula, displayed structural formula and skeletal formula for ...

1,1,1,2-tetrafluoroethane, 1,1,1,2-tetrachloroethane, 1,1,1,2-tetrabromoethane, 1,1,1,2-tetraiodoethane

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

 

(2) X2CHCHX2, 1,1,2,2-tetrafluoroethane, 1,1,2,2-tetrachloroethane, 1,1,2,2-tetrabromoethane, 1,1,2,2-tetraiodoethane condensed constitutional structural formula skeletal formula , where X = F, Cl, Br or I

The abbreviated structural formula, displayed structural formula and skeletal formula for ...

1,1,2,2-tetrafluoroethane, 1,1,2,2-tetrachloroethane, 1,1,2,2-tetrabromoethane, 1,1,2,2-tetraiodoethane

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

Symmetrical molecule

 

There are only 2 distinct constitutional isomers of formula C2H2X4 (where X = halogen atom)

Both of these isomers are derived from the tetrahalo-substitution of the alkane hydrocarbon of formula C2H6 (ethane) with fluorine, chlorine, bromine or iodine.

Summary of key points and extra notes on the isomers of molecular formulae

C2H2F4, C2H2Cl4, C2H2Br4 and C2H2I4

 Isomerism: Only Positional Isomerism

Each compound with the formula C2H2X4 (X = F, Cl, Br, I) is a fully saturated ethane derivative, not an alkene. That means:

  • No C=C double bond → no restricted rotation

  • No stereocentres  e.g. chiral carbon → no optical isomerism

  • No geometrical (cis-trans) isomerism

Instead, each exhibits only positional isomerism, based on how the halogen atoms are distributed across the two carbon atoms.

Structural Positional Isomers for Each Formula

Molecular Formula

Isomer 1

Isomer 2

C2H2F4

1,1,2,2-tetrafluoroethane

1,1,1,2-tetrafluoroethane

C2H2Cl4

1,1,2,2-tetrachloroethane

1,1,1,2-tetrachloroethane

C2H2Br4

1,1,2,2-tetrabromoethane

1,1,1,2-tetrabromoethane

C2H2I4

1,1,2,2-tetraiodoethane

1,1,1,2-tetraiodoethane

Each pair differs in the distribution of halogens between the two carbon atoms:

  • 1,1,2,2-: symmetrical substitution

  • 1,1,1,2-: asymmetrical substitution

Physical Property Differences of C2H2F4, C2H2Cl4, C2H2Br4 and C2H2I4

Property

1,1,2,2-Isomer

1,1,1,2-Isomer

Polarity

Lower (more symmetrical)

Higher (more polar)

Boiling Point

Slightly lower

Slightly higher

Dipole Moment

Near zero

Non-zero

Solubility in polar solvents

Lower

Higher

Chemical Property Differences of C2H2F4, C2H2Cl4, C2H2Br4 and C2H2I4

  • Reactivity: Slightly higher for the more polar 1,1,1,2-isomers in nucleophilic substitution.

  • Stability: Both are stable, but symmetrical isomers may be less reactive due to lower dipole moment.

Uses of C2H2F4, C2H2Cl4, C2H2Br4 and C2H2I4

Compound

Typical Use

C2H2F4

Refrigerants (e.g. HFC-134a)

C2H2Cl4

Former solvent (now phased out due to toxicity)

C2H2Br4

Density-based mineral separation

C2H2I4

Rarely used; sometimes in radiopaque agents

Misconceptions to Avoid when study the isomers of C2H2F4 , C2H2Cl4 , C2H2Br4 or C2H2I4

  • “Tetrahalogenated ethanes can show cis-trans isomerism” → Only possible in alkenes, not saturated ethanes.

  • “More halogens = more isomers” → Not necessarily; symmetry limits possibilities.

  • “All positional isomers have similar properties” → Polarity and symmetry matter!

Exam Tips for questions that may involve isomers of C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

  • Focus on halogen placement across the two carbon atoms.

  • Use IUPAC naming to distinguish isomers clearly.

  • Highlight dipole moment and symmetry when comparing properties.

  • Don’t confuse these with tetrahalogenated ethenes (C2X4), which can show geometrical stereoisomerism.

More on uses of these tetrahalogenated compounds

Especially those based on ethane and methane frameworks — have found diverse applications across industrial, medical, and environmental domains, largely due to their chemical stability, volatility, and unique physical properties. Here's a structured overview:

Key Practical Applications of C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

Compound Type

Example

Applications

Tetrafluoroethane (C2H2F4)

HFC-134a

Refrigerants in air conditioners and refrigerators; propellants in aerosol sprays

Tetrachloroethane (C2H2Cl4)

1,1,2,2- and 1,1,1,2-isomers

Industrial solvents; intermediate in chemical synthesis

Tetrabromoethane (C2H2Br4)

Heavy liquid separation

Used in mineral separation due to high density; niche organic synthesis

Tetraiodoethane (C2H2I4)

Radiopaque agents

Occasionally used in medical imaging; limited due to instability

Why C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4 are Useful

  • High density: Especially for brominated and iodinated compounds — useful in separation techniques.

  • Chemical inertness: Fluorinated compounds resist degradation, making them ideal for harsh environments.

  • Volatility and low flammability: Useful in refrigerants and propellants.

  • Radiopacity: Iodinated compounds absorb X-rays, aiding in medical diagnostics.

Environmental and Safety Considerations for C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

  • Many tetrahalogenated compounds are persistent pollutants and can bioaccumulate.

  • CFCs and HFCs (e.g. tetrafluoroethane) contribute to ozone depletion and global warming, leading to regulatory phase-outs.

  • Carbon tetrachloride and tetrachloroethane are toxic and carcinogenic, now heavily restricted.

Learning objectives - questions to be answered?

How do you draw the structural formula and skeletal formula of the isomers of molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

How many aliphatic structural isomers are there of halogen compounds with molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

How many aliphatic carbon chain isomers are there of halogen compounds with molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

How many positional isomers are there of organic halogen molecules with molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

How many E/Z (geometrical) isomers are there of molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

How many R/S (optical) isomers (enantiomers) of molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Are there any cyclic haloalkene isomers of formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Are there any cyclo haloalkane isomers of formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Are there any halodiene isomers of molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Are there any haloalkyne isomers of molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Are there any functional group isomers with a molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Do C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4 organic halogen molecules have any stereoisomers?

Are there any E/Z (geometrical) isomers with a molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

Are there any R/S (optical) isomers (enantiomers) with a molecular formula C2H2Cl4 C2H2Br4 C2H2F4 C2H2I4?

This page will answer these questions for molecular formulae C2H2F4 , C2H2Cl4 , C2H2Br4 and C2H2I4

Associated organic chemistry  links

Index of sets of isomers for a given molecular formula

The molecular structure and naming of HALOALKANES (how to name and draw alkane structures)

Index of revision notes on the chemistry HALOALKANES including reactions

 Advanced Level pre-university organic chemistry notes

 IR, mass and H-1 and C-13 NMR spectra of organic compounds

For isomerism in organic chemistry, see also the notes

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

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

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

 This is a big chemistry website, please allow time to explore it

A summary chart of isomerism

index for all isomerism pages

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