isomers of C5H7F , C5H7Cl , C5H7Br and C5H7I

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Advanced level organic chemistry PART 14.7: Structural isomers of molecular formula C5H7X (X = halogen)

Doc Brown's Advanced Chemistry: Part 14.7

57+ examples of the constitutional structural isomers of molecular formula C5H7F, C5H7Cl, C5H7Br and C5H7I

[Author ©  Dr WP Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK advanced level chemistry courses, IB advanced chemistry & US K12 grades 11-12 and AP honors chemistry courses: Molecular spectroscopy and analysing the isomers of C5H7X [updated Feb 23rd 2026 *]

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Introduction to the selected constitutional-structural isomers and stereoisomers of molecular formula C5H7X (X = halogen)

Relative molecular mass and percent composition of C5H7X (X = halogen) 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
C5H7F 86.13 69.73 8.21 22.06
C5H7Cl 102.58 58.55 6.89 34.56
C5H7Br 147.03 40.85 4.81 54.34
C5H7I 194.03 30.96 3.64 65.40

Empirical formula = molecular formula = C5H7X (where X = a single halogen atom)

52selected constitutional isomers of C5H7Cl, C5H7Br, C5H7I or C5H7F skeletal formula types of isomerism how to analysise C5H7Cl C5H7Br C5H7I C5H7F for alkenes alkynes E/Z geometrical isomers R/S optical isomers positional isomers of C5H7Cl, C5H7Br, C5H7I or C5H7F

Apologies for the order of text and images, isomers 28 to 57 were an after thought, but some quite interesting theoretical structures, some of which actually exist!

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 atoms), (b) change in position of a substituent or functional group and (c) functional group isomerism where the atoms have a different connectivity configuration, usually with significant differences in chemical and physical properties e.g.

In terms of isomers of C5H7X there are

(a) chain variations based on the open chain aliphatic linear and branched and also a huge variety of alicyclic structures,

(b) positional isomers e.g. the -X halogen groups in all of the molecules,

(c) most are all functional group isomers of each other e.g. unsaturated open chain alkenes and alkynes versus cyclic alkenes and saturated bicyclic molecules.

Stereoisomerism - isomers based on the same connectivity of the atoms (same constitutional formula), but in some way, they are 2D or 3D spatially different non-superimposable images (e.g. E/Z 'geometrical' 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.

For stereoisomers, the (CIP) abbreviation means the IUPAC Cahn-Ingold-Prelog priority order rule for assigning E/Z (geometrical) and R/S (optical) stereoisomers.

E/Z stereoisomerism was called 'geometrical isomerism' e.g. cis and trans isomers of alkenes or disubstituted cyclic alkanes where there are 2D/3D spatial variations that are not mirror images and not super imposable.

Many examples in both the open chain aliphatic and alicyclic compounds sometimes overlapping with R/S optical isomers for the same molecule!

R/S stereoisomerism was called 'optical isomerism', the pairs of isomers are called enantiomers which are 3D non-superimposable mirror image forms of the molecule (enantiomers). The molecule must have a chiral centre (a stereocentre), that is an asymmetric carbon atom with four different atoms/groups attached to it.

Again many examples in both the open chain aliphatic and alicyclic compounds and again sometimes overlapping with E/Z geometrical isomers for the same molecule!

NOTE

Some of the C5H7X (X = halogen) isomers described may be highly reactive and very thermodynamically unstable e.g. due to weak highly strained bonds in cyclic compounds or bulky groups like iodine atoms (which also the weakest of the C-halogen bonds) and some may not even exist at all (except theoretically of course!).

I've identified at least 57+ constitutional isomers and at least 33+ pairs of E/Z geometrical or R/S optical isomers for the molecular formulae C5H7F, C5H7Cl, C5H7Br or C5H7I

So, theoretically there are at least 90+ distinct isomers of C5H7F, C5H7Cl, C5H7Br or C5H7I.

I'm not expert enough to name all these isomers, though made some attempts, but, since I'm a pre-university chemistry website, I'm not to fussed about the names, because of these 'types' of isomers would only

Details of the selected constitutional isomers and stereoisomers of molecules with formulae

C5H7F, C5H7Cl, C5H7Br and C5H7I

Some of the C5H7X (X = halogen) isomers described may be highly reactive and very thermodynamically unstable e.g. due to weak highly strained bonds and some may not even exist at all (except theoretically of course!).

(1) 1-fluorocyclopentene, 1-chlorocyclopentene, 1-bromocyclopentene, 1-iodocyclopentene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (halogenated cyclopentene),

1-fluorocyclopentene,  1-chlorocyclopentene,  1-bromocyclopentene,  1-iodocyclopentene

1-fluorocyclopent-1-ene,  1-chlorocyclopent-1-ene,  1-bromocyclopent-1-ene,  1-iodocyclopent-1-ene

 

(2) R/S optical isomers 3-fluorocyclopentene, 3-chlorocyclopentene, 3-bromocyclopentene, 3-iodocyclopentene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclopentene), a secondary haloalkane

3-fluorocyclopentene,  3-chlorocyclopentene,  3-bromocyclopentene,  3-iodocyclopentene

3-fluorocyclopent-1-ene,  3-chlorocyclopent-1-ene,  3-bromocyclopent-1-ene,  3-iodocyclopent-1-ene

Exhibits R/S optical isomerism, the ring C3 of the C-X bond is asymmetric (chiral)

 

(3) 4-fluorocyclopentene, 4-chlorocyclopentene, 4-bromocyclopentene, 4-iodocyclopentene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclopentene), a secondary haloalkane

4-fluorocyclopentene,  4-chlorocyclopentene,  4-bromocyclopentene,  4-iodocyclopentene

4-fluorocyclopent-1-ene,  4-chlorocyclopent-1-ene,  4-bromocyclopent-1-ene,  4-iodocyclopent-1-ene

 

(4) 1-fluoro-2-methylcyclobutene, 1-chloro-2-methylcyclobutene, 1-bromo-2-methylcyclobutene, 1-iodo-2-methylcyclobutene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclobutene) and haloalkene

1-fluoro-2-methylcyclobutene,  1-chloro-2-methylcyclobutene,  1-bromo-2-methylcyclobutene,  1-iodo-2-methylcyclobutene

 

(5) R/S optical isomers 3-fluoro-1-methylcyclobutene, 3-chloro-1-methylcyclobutene, 3-bromo-1-methylcyclobutene, 3-iodo-1-methylcyclobutene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclobutene) and secondary haloalkane.

3-fluoro-1-methylcyclobutene,  3-chloro-1-methylcyclobutene,  3-bromo-1-methylcyclobutene,  3-iodo-1-methylcyclobutene

3-fluoro-1-methylcyclobut-1-ene,  3-chloro-1-methylcyclobut-1-ene,  3-bromo-1-methylcyclobut-1-ene,  3-iodo-1-methylcyclobut-1-ene

Exhibits R/S optical isomerism, the C3 of the C-X bond is asymmetric (chiral)

 

(6) R/S optical isomers 4-fluoro-1-methylcyclobutene, 4-chloro-1-methylcyclobutene, 4-bromo-1-methylcyclobutene, 4-iodo-1-methylcyclobutene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclobutene) and secondary haloalkane.

4-fluoro-1-methylcyclobutene,  4-chloro-1-methylcyclobutene,  4-bromo-1-methylcyclobutene,  4-iodo-1-methylcyclobutene

4-fluoro-1-methylcyclobut-1-ene,  4-chloro-1-methylcyclobut-1-ene,  4-bromo-1-methylcyclobut-1-ene,  4-iodo-1-methylcyclobut-1-ene

Exhibits R/S optical isomerism, the C4 of the C-X bond is asymmetric (chiral)

 

(7) R/S optical isomers 1-fluoro-3-methylcyclobutene, 1-chloro-3-methylcyclobutene, 1-bromo-3-methylcyclobutene, 1-iodo-3-methylcyclobutene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclobutene) and secondary haloalkane.

1-fluoro-3-methylcyclobutene,  1-chloro-3-methylcyclobutene,  1-bromo-3-methylcyclobutene,  1-iodo-3-methylcyclobutene

1-fluoro-3-methylcyclobut-1-ene,  1-chloro-3-methylcyclobut-1-ene,  1-bromo-3-methylcyclobut-1-ene,  1-iodo-3-methylcyclobut-1-ene

Exhibits R/S optical isomerism, the C3 of the C-CH3 bond is asymmetric (chiral)

 

(8) R/S optical E/Z geometrical isomers 3-fluoro-4-methylcyclobutene, 3-chloro-4-methylcyclobutene, 3-bromo-4-methylcyclobutene, 3-iodo-4-methylcyclobutene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclobutene) and secondary haloalkane.

3-fluoro-4-methylcyclobutene,  3-chloro-4-methylcyclobutene,  3-bromo-4-methylcyclobutene,  3-iodo-4-methylcyclobutene

3-fluoro-4-methylcyclobut-1-ene,  3-chloro-4-methylcyclobut-1-ene,  3-bromo-4-methylcyclobut-1-ene,  3-iodo-4-methylcyclobut-1-ene

Exhibits R/S optical isomerism, the two right carbon atoms of the ring are asymmetric (C3 and C4 are chiral) and this overlaps with E/Z geometrical isomerism - complicated, university level analysis.

CIP assignment priority rule for stereoisomers: ZX >  6C6C  >  6C1H > 1H (X = halogen, Z = 9, 17, 35 or 53)

 

(9) R/S optical 2-fluoro-3-methylcyclobutene, 2-chloro-3-methylcyclobutene, 2-bromo-3-methylcyclobutene, 2-iodo-3-methylcyclobutene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted cycloalkene (cyclobutene) and haloalkene.

2-fluoro-3-methylcyclobutene,  2-chloro-3-methylcyclobutene,  2-bromo-3-methylcyclobutene,  2-iodo-3-methylcyclobutene

2-fluoro-3-methylcyclobut-1-ene,  2-chloro-3-methylcyclobut-1-ene,  2-bromo-3-methylcyclobut-1-ene,  2-iodo-3-methylcyclobut-1-ene

Exhibits R/S optical isomerism, the C3 of the C-CH3 bond is asymmetric (chiral)

CIP assignment priority rule for E/Z or R/S isomers:6CZX  >   6C6C  >  6C1H > 1H (X = halogen, Z = 9, 17, 35 or 53)

 

(10) 3-fluoro-1,2-dimethylcyclopropene, 3-chloro-1,2-dimethylcyclopropene, 3-bromo-1,2-dimethylcyclopropene, 3-iodo-1,2-dimethylcyclopropene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a trisubstituted cycloalkene (cyclopropene) and secondary haloalkane

3-fluoro-1,2-dimethylcyclopropene, 3-chloro-1,2-dimethylcyclopropene,  3-bromo-1,2-dimethylcyclopropene,  3-iodo-1,2-dimethylcyclopropene

 

(11) 1-(fluoromethyl)-2-methylcyclopropene, 1-(chloromethyl)-2-methylcyclopropene, 1-(bromomethyl)-2-methylcyclopropene, 1-(iodomethyl)-2-methylcyclopropene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a disubstituted cycloalkene (cyclopropene) and primary haloalkane

1-(fluoromethyl)-2-methylcyclopropene,  1-(chloromethyl)-2-methylcyclopropene,  1-(bromomethyl)-2-methylcyclopropene,  1-(iodomethyl)-2-methylcyclopropene

 

(12) R/S optical isomers 1-fluoro-2,3-dimethylcyclopropene, 1-chloro-2,3-dimethylcyclopropene, 1-bromo-2,3-dimethylcyclopropene, 1-iodo-2,3-dimethylcyclopropene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a trisubstituted cycloalkene (cyclopropene) and haloalkene

1-fluoro-2,3-dimethylcyclopropene, 1-chloro-2,3-dimethylcyclopropene,  1-bromo-2,3-dimethylcyclopropene,  1-iodo-2,3-dimethylcyclopropene

Exhibits R/S optical isomerism, the top carbon atom C3 of the ring is asymmetric (chiral).

 

(13) R/S optical isomers 3-(fluoromethyl)-1-methylcyclopropene, 1-(chloromethyl)-2-methylcyclopropene, 1-(bromomethyl)-2-methylcyclopropene, 1-(iodomethyl)-2-methylcyclopropene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a disubstituted cycloalkene (cyclopropene) and primary haloalkane

3-(fluoromethyl)-1-methylcyclopropene,  1-(chloromethyl)-2-methylcyclopropene,  1-(bromomethyl)-2-methylcyclopropene,  1-(iodomethyl)-2-methylcyclopropene

Exhibits R/S optical isomerism, the top ring C3 of the C-CH2X bond is asymmetric (chiral)

 

(14) 1-fluoro-3,3-dimethylcyclopropene, 1-chloro-3,3-dimethylcyclopropene, 1-bromo-3,3-dimethylcyclopropene, 1-iodo-3,3-dimethylcyclopropene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a trisubstituted cycloalkene (cyclopropene) and haloalkene.

1-fluoro-3,3-dimethylcyclopropene, 1-chloro-3,3-dimethylcyclopropene,  1-bromo-3,3-dimethylcyclopropene,  1-iodo-3,3-dimethylcyclopropene

 

(15) 1-fluoropent-1-yne, 1-chloro-pent-1-yne, 1-bromopent-1-yne, 1-iodo-pent-1-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted linear alkyne and haloalkyne

1-fluoropent-1-yne,  1-chloro-pent-1-yne,  1-bromopent-1-yne,  1-iodo-pent-1-yne

 

(16) R/S isomers 3-fluoropent-1-yne, 3-chloro-pent-1-yne, 3-bromopent-1-yne, 3-iodo-pent-1-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted linear alkyne and secondary haloalkane group.

3-fluoropent-1-yne,  3-chloro-pent-1-yne,  3-bromopent-1-yne,  3-iodo-pent-1-yne

Exhibits R/S optical isomerism, carbon atom C3 is asymmetric (chiral)

 

(17) R/S optical isomers 4-fluoropent-1-yne, 4-chloro-pent-1-yne, 4-bromopent-1-yne, 4-iodo-pent-1-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted linear alkyne and secondary haloalkane group.

4-fluoropent-1-yne,  4-chloro-pent-1-yne,  4-bromopent-1-yne,  4-iodo-pent-1-yne

Exhibits R/S optical isomerism, carbon atom C4 is asymmetric (chiral)

CIP assignment priority rule for R/S isomers: ZX >  6C6C  >  6C1H > 1H (X = halogen, Z = 9, 17, 35 or 53)

 

(18) 5-fluoropent-1-yne, 5-chloro-pent-1-yne, 5-bromopent-1-yne, 5-iodo-pent-1-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I a substituted linear alkyne and primary haloalkane group.

5-fluoropent-1-yne,  5-chloropent-1-yne,  5-bromopent-1-yne,  5-iodopent-1-yne

 

(19) 1-fluoropent-2-yne, 1-chloro-pent-2-yne, 1-bromopent-2-yne, 1-iodo-pent-2-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a substituted linear alkyne and primary haloalkane group.

1-fluoropent-2-yne,  1-chloro-pent-2-yne,  1-bromopent-2-yne,  1-iodo-pent-2-yne

 

(20) R/S optical isomers 4-fluoropent-2-yne, 4-chloro-pent-2-yne, 4-bromopent-2-yne, 4-iodo-pent-2-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a substituted linear alkyne and secondary haloalkane group.

4-fluoropent-2-yne,  4-chloro-pent-2-yne,  4-bromopent-2-yne,  4-iodo-pent-2-yne

Exhibits R/S optical isomerism, carbon atom C4 is asymmetric (chiral)

CIP assignment priority rule for R/S isomers: ZX >  6C6C  >  6C1H > 1H (X = halogen, Z = 9, 17, 35 or 53)

 

(21) 5-fluoropent-2-yne, 5-chloro-pent-2-yne, 5-bromopent-2-yne, 5-iodo-pent-2-yne skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a substituted linear alkyne and primary haloalkane group.

5-fluoropent-2-yne,  5-chloropent-2-yne,  5-bromopent-2-yne,  5-iodo-pent-2-yne

 

(22) E/Z geometrical isomers 1-fluoropenta-1,3-diene, 1-chloropenta-1,3-diene, 1-bromopenta-1,3-diene, 1-iodoropenta-1,3-diene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a substituted linear diene, haloalkene

1-fluoropenta-1,3-diene,  1-chloropenta-1,3-diene,  1-bromopenta-1,3-diene,  1-iodoropenta-1,3-diene

This exhibits E/Z geometrical isomerism, the diagram shows the isomers based on 1-ene group, but the 3-ene alkene group is also a cause of E/Z isomers. Therefore we have two E/Z geometrical stereocentres in the same molecule, which gives four possibilities of E/Z stereoisomers i.e. EE', EZ', E'Z and ZZ'.

CIP assignment priority rule for E/Z isomers: ZX > 6C6C  >  6C1H > 1H

CIP rule about the >C=C< double bonds, (X = halogen, Z = 9, 17, 35 or 53)

You can also have, but not shown:

2-fluoropenta-1,3-diene,  2-chloropenta-1,3-diene,  2-bromopenta-1,3-diene,  2-iodopenta-1,3-diene

but these will only give one pair of E/Z geometrical isomers.

 

(23) 3-fluoropenta-1,3-diene, 3-chloropenta-1,3-diene, 3-bromopenta-1,3-diene, 3-iodoropenta-1,3-diene E/Z geometrical isomers skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a halogen substituted linear diene

3-fluoropenta-1,3-diene,  3-chloropenta-1,3-diene,  3-bromopenta-1,3-diene,  3-iodoropenta-1,3-diene

This exhibits E/Z geometrical isomerism based on the 3-ene alkene group.

CIP assignment priority rule for E/Z isomers: ZX > 6C6C  >  6C1H > 1H

CIP rule about the >C=C< double bond, (X = halogen, Z = 9, 17, 35 or 53)

You can also have, but not shown:

2-fluoropenta-1,3-diene,  2-chloropenta-1,3-diene,  2-bromopenta-1,3-diene,  2-iodoropenta-1,3-dienen

4-fluoropenta-1,3-diene,  4-chloropenta-1,3-diene,  4-bromopenta-1,3-diene,  4-iodoropenta-1,3-dienen

5-fluoropenta-1,3-diene,  5-chloropenta-1,3-diene,  5-bromopenta-1,3-diene,  5-iodoropenta-1,3-dienen

 

(24) stereoisomers 1-fluoropenta-1,2-diene, 1-chloropenta-1,2-diene, 1-bromopenta-1,2-diene, 1-iodopenta-1,2-diene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a halogen substituted linear diene

1-fluoropenta-1,2-diene,  1-chloropenta-1,2-diene,  1-bromopenta-1,2-diene,  1-iodopenta-1,2-diene

This exhibits an 'unusual' R/S (optical) stereoisomerism and has non-superimposable mirror image forms because the orbitals of the alkene pi bonds are at 90o to each other.

You can also have, but not shown:

3-fluoropenta-1,2-diene,  3-chloropenta-1,2-diene,  3-bromopenta-1,2-diene,  3-iodopenta-1,2-diene

 

(25) R/S optical isomers 4-fluoropenta-1,2-diene, 4-chloropenta-1,2-diene, 4-bromopenta-1,2-diene, 4-iodopenta-1,2-diene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a halogen substituted linear diene

4-fluoropenta-1,2-diene,  4-chloropenta-1,2-diene,  4-bromopenta-1,2-diene,  4-iodopenta-1,2-diene

These molecules exhibit R/S optical isomerism because carbon atom 4 is asymmetric (chiral).

You can also have, but not shown:

5-fluoropenta-1,2-diene,  5-chloropenta-1,2-diene,  5-bromopenta-1,2-diene,  5-iodopenta-1,2-diene

1-fluoropenta-2,3-diene,  1-chloropenta-2,3-diene,  1-bromopenta-2,3-diene,  1-iodopenta-2,3-diene

2-fluoropenta-2,3-diene,  2-chloropenta-2,3-diene,  2-bromopenta-2,3-diene,  2-iodopenta-2,3-diene

 

(26) E/Z isomers 1-fluoropenta-1,4-diene, 1-chloropenta-1,4-diene, 1-bromopenta-1,4-diene, 1-iodoropenta-1,4-diene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a halogen substituted linear diene

1-fluoropenta-1,4-diene,  1-chloropenta-1,4-diene,  1-bromopenta-1,4-diene,  1-iodoropenta-1,4-diene

This exhibits E/Z geometrical isomerism based on the 1-ene alkene group.

CIP assignment priority rule for E/Z isomers: ZX > 6C6C  >  6C1H > 1H

CIP rule about the >C=C< double bond, (X = halogen, Z = 9, 17, 35 or 53)

You can also have, but not shown:

2-fluoropenta-1,4-diene,  2-chloropenta-1,4-diene,  2-bromopenta-1,4-diene,  2-iodoropenta-1,4-diene

 

(27) 3-fluoropenta-1,4-diene, 3-chloropenta-1,4-diene, 3-bromopenta-1,4-diene, 3-iodoropenta-1,4-diene skeletal formula constitutional structural formuka molecular formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers a halogen substituted linear diene

3-fluoropenta-1,4-diene,  3-chloropenta-1,4-diene,  3-bromopenta-1,4-diene,  3-iodoropenta-1,4-diene

 

(28) 3-fluoro-3-methylcyclbut-1-ene, 3-chloro-3-methylcyclobut-1-ene, 3-bromo-3-methylcyclobut-1-ene, 3-iodo-3-methylcyclobut-1-ene skeletal formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers , cycloalkene and tertiary haloalkane

3-fluoro-3-methylcyclbut-1-ene,  3-chloro-3-methylcyclobut-1-ene,  3-bromo-3-methylcyclobut-1-ene,  3-iodo-3-methylcyclobut-1-ene.

R/S optical isomers because the ring C3 of C-X bond is chiral.

 

(29-33) halo-alkyl-cyclopropenes skeletal formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers

(29) 3-fluoro-1,3-dimethylcyclopropene,  3-chloro-1,3-dimethylcyclopropene,  3-bromo-1,3-dimethylcyclopropene,  3-iodo-1,3-dimethylcyclopropene.

R/S optical isomers due to top C3 of the Δ being chiral (asymmetric C atom).

(30) 1-(fluoromethyl)-3-methylcyclopropene,  1-(chloromethyl)-3-methylcyclopropene,  1-(bromomethyl)-3-methylcyclopropene,  1-(iodomethyl)-3-methylcyclopropene

R/S optical isomers due to top C3 of the Δ being chiral (asymmetric C atom).

(31) 3-(fluoromethyl)-3-methylcyclopropene,  3-(chloromethyl)-3-methylcyclopropene,  3-(bromomethyl)-3-methylcyclopropene,  3-(iodomethyl)-3-methylcyclopropene

(32) names?:  1-(2-fluoroethyl)cyclopropene,  1-(2-chloroethyl)cyclopropene,  1-(2-bromoethyl)cyclopropene,  1-(2-iodoethyl)cyclopropene

(33)names?:  3-(2-fluoroethyl)cyclopropene,  3-(2-chloroethyl)cyclopropene,  3-(2-bromoethyl)cyclopropene,  3-(2-iodoethyl)cyclopropene

You can also have theoretically, but not shown:

1-(1-haloethyl)cyclopropenes  and  3-(1-haloethyl)cyclopropenes, again names?

 

(34-36) halo-alkyl-butynes skeletal formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers  X = F, Cl, Br, I

These halogenated propynes have two functional groups: halide (C-X) and alkyne (C≡C)

(34) (CH3)2CHC≡CX,  1-fluoro-3-methylbut-1-yne,  1-chloro-3-methylbut-1-yne,  1-bromo-3-methylbut-1-yne,  1-iodo-3-methylbut-1-yne

(35) (CH3)2CClC≡CH,  3-fluoro-3-methylbut-1-yne,  3-chloro-3-methylbut-1-yne,  3-bromo-3-methylbut-1-yne,  3-iodo-3-methylbut-1-yne

(36) XCH2CH(CH3)C≡CH,  4-fluoro-3-methylbut-1-yne,  4-chloro-3-methylbut-1-yne,  4-bromo-3-methylbut-1-yne,  4-iodo-3-methylbut-1-yne

 

(37-40) halo-alkyl-cyclopropyl alkenes skeletal formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers

(37) 1-halo-2-methylcyclopropylethene, these exhibit E/Z geometrical isomerism

e.g. [(1E or 1Z)-2-chloroethenyl]cyclopropane, 1-chloro-2-cyclopropylethene

CIP assignment priority rule for E/Z or R/S isomers: ZX >  6C  > 1H (X = halogen, Z = 9, 17, 35 or 53)

(38) names?: 1-fluoro-1-cyclopropylethene,  1-chloro-1-cyclopropylethene,  1-bromo-1-cyclopropylethene,  1-iodo-1-cyclopropylethene,

(39) names?: 1-fluoro-1-ethenylcyclopropane,  1-chloro-1-ethenylcyclopropane, 1-bromo-1-ethenylcyclopropane,  1-iodo-1-ethenylcyclopropane

(40) names?: 2-fluoro-1-ethenylcyclopropane,  2-chloro-1-ethenylcyclopropane, 2-bromo-1-ethenylcyclopropane,  2-iodo-1-ethenylcyclopropane

 

(41-46) These have part of an alkene group (methylene) which is also part of the cyclopropane ring and all have the haloalkane group in various positions i.e. in a side chain of the ring, directly attached to the ring or attached to the alkene group.

halo-methylenecyclopropanes skeletal formula C5H7F, C5H7Cl, C5H7Br, C5H7I isomers

Examples (41)-(46) would only be encountered at university level.

(41) names?: e.g. 1-(chloromethyl)-2-methylidenecyclopropane,  1-(chloromethyl)-2-methylenecyclopropane

These exhibit R/S optical isomerism because to the top C of the Δ is chiral.

(42) names?: e.g. 1-chloro-2-methyl-3-methylenecyclopropane

These exhibit R/S optical isomerism because to the top and bottom carbons of the Δ are chiral.

This is very complex stereoisomerism because there are two R/S chiral centres AND E/Z geometrical isomerism because the -CH3 and -X can be at different positions above and below the ring.

(43) names?: e.g. 1-chloro-2-ethylidenecyclopropane

These exhibit R/S optical isomerism because to the top and bottom carbons of the Δ are chiral.

Not sure on E/Z geometrical isomerism?

(44) names?: e.g.

These exhibit R/S optical isomerism because to the top and bottom carbons of the Δ are chiral.

Not sure on E/Z geometrical isomerism?

(45) names?: e.g. 1-chloro-1-methyl-2-methylenecyclopropane

These exhibit R/S optical isomerism because to the top and bottom carbons of the Δ are chiral.

(46) names?:

 

(47-52) These are halogen substituted saturated 'bicyclo' alkanes

halogenated bicycloalkanes C5H7F, C5H7Cl, C5H7Br, C5H7I skeletal formula

(47) names?: e.g. 1-chlorospiro[2.2]pentane, secondary haloalkanes, R/S optical isomers

(48) names ?, secondary haloalkanes

(49) names?: e.g. 1-chlorobicyclo[2.1.0]pentane, tertiary haloalkanes, R/S optical isomers

(50) names ?, secondary haloalkanes, R/S optical isomers

(51) names?: e.g. 1-chlorobicyclo[1.1.1]pentane, a tertiary haloalkane

(52) names ?, secondary haloalkanes

 

(53-57) based on methylbuta-1,2-diene or methylbuta-1,3-diene

halogenated buta-1,2-dienes & halogen substituted buta-1,3-dienes C5H7F, C5H7Cl, C5H7Br, C5H7I isomers

(53) 1-chloro-3-methylbuta-1,2-diene

(54) 4-chloro-3-methylbuta-1,2-diene

(55) 1-chloro-2-methylbuta-1,3-diene, E/Z geometrical isomers

CIP assignment priority rule for E/Z isomers: ZX >  6C6C  >  6C1H > 1H

CIP rule about the >C=C< double bond, (X = halogen, Z = 9, 17, 35 or 53)

(56) 2-chloro-3-methylbuta-1,3-diene

(57) 1-chloro-3-methylbuta-1,3-diene, E/Z geometrical isomers

CIP assignment priority rule for E/Z isomers: ZX >  6C1H > 1H

CIP rule about the >C=C< double bond, (X = halogen, Z = 9, 17, 35 or 53)

Extra information on some of the uses and applications of these isomers (just out of curiosity!)

Isomers of C5H7X (where X = F, Cl, Br, I) are typically halogenated cyclopentenes or pentynes, and their uses span synthetic intermediates, pharmaceuticals, agrochemicals, and materials science.

Their reactivity and applications depend on both the halogen and the position of their substitution.

General Applications of C5H7X Isomers

  • Pharmaceutical intermediates: Fluorinated alkenes are used to modify bioactivity and metabolic stability.

  • Polymer precursors: Fluorocyclopentenes are used in specialty polymers with enhanced thermal or chemical resistance.

  • Radiolabeling: Fluorine-18 analogs are used in PET imaging. | | Chlorine (C5H7Cl) | Chlorocyclopentene, 1-chloropentene |

  • Agrochemical synthesis: Chlorinated alkenes serve as precursors to herbicides and fungicides.

  • Cross-coupling reactions: Used in Suzuki and Heck reactions for building complex molecules.

  • Solvent modifiers: Some isomers are used to tailor solvent polarity in industrial processes. | | Bromine (C5H7Br) | Bromocyclopentene, 1-bromopentene |

  • Grignard reagent precursors: Useful in organometallic synthesis.

  • Pharmaceutical building blocks: Brominated alkenes are used to introduce reactive handles for further derivatization.

  • Flame retardants: Some brominated compounds are used in polymer additives. | | Iodine (C5H7I) | Iodocyclopentene, 1-iodopentene |

  • Radioiodination: Iodine-125 and Iodine-131 analogs are used in radiopharmaceuticals.

  • Cross-coupling chemistry: Excellent leaving group in palladium-catalyzed reactions.

  • Synthetic intermediates: Used to introduce iodine into complex organic frameworks. |

Structural Diversity and Reactivity

  • Aliphatic versus cyclic: Isomers may be straight-chain (e.g. 1-halopentene) or cyclic (e.g. halocyclopentene), affecting their reactivity and physical properties.

  • Position of halogen: Primary, secondary, or allylic halides differ in nucleophilicity and stability.

  • Stereoisomers: Cis/trans isomers of cyclopentenes influence biological activity and synthetic utility.

Research and Niche Uses

  • Medicinal chemistry: Halogenated alkenes are explored for antiviral, anticancer, and anti-inflammatory properties.

  • Material science: Fluorinated and brominated isomers are used in liquid crystals and specialty coatings.

  • Environmental chemistry: Some isomers are studied for degradation pathways and atmospheric reactivity.

A summary chart of isomerism

index for all isomerism pages

Associated organic chemistry  links

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 isomerism)

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

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

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

Index of advanced (pre-university) organic chemistry revision notes

 The chemistry of alkanes and the petrochemical industry

 The chemistry of alkenes

 The chemistry of organic halogen compounds

 The chemistry of alcohols

The chemistry of aldehydes and ketones

 The chemistry of carboxylic acids and derivatives

The chemistry of organo-nitrogen compounds

The chemistry of aromatic compounds

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