Cyclopropyl group

Chemical structure derived from cyclopropane

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Chemical structure of the cyclopropyl group

A cyclopropyl group is a chemical structure derived from cyclopropane; it is typically produced in a cyclopropanation reaction. The group has an empirical formula of C3H5 and chemical bonds from each of the three carbons to both of the other two.

## Structure and bonding

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Due to the unfavoured bond angles (60°), cyclopropyl groups are highly strained. Two orbital models were proposed to describe the bonding situation. The Coulson-Moffit model uses bent bonds. The C-C bonds are formed by overlap of two sp-hybrid orbitals. To adapt to the small bond angle, there is some rehybridization resulting in sp~5-hybrids for the ring bonds and sp~2 for the C-H bonds. This model resembles the banana bond model for C=C double bonds (τ bonds).

Alternatively the structure can be explained with the Walsh model. Here the two sp-hybrids forming the ring bond are separated into one sp2-hybrid and one pure p-orbital. This corresponds to the π bond description of C=C double bonds.

Cyclopropyl groups are good donors in hyperconjugation resulting in a considerable stabilization of carbocations. In contrast to double bonds, stabilization of radicals is weaker and stabilization of carbanions is negligible. This is explained by the occupation of the π system with two more electrons, making the cyclopropyl methyl cation's HOMO isolobal to the allyl anion's HOMO.[1]

## References

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1. ^ Jung, Sebastian T.; Nickisch, Roman; Reinsperger, Tony; Luy, Burkhard; Podlech, Joachim (April 2021). "Stereoelectronic effects: Perlin effects in cyclohexane‐derived compounds". Journal of Physical Organic Chemistry. 34 (4). doi:10.1002/poc.4165. S2CID 229407105.

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* t
* e

Functional groups

Hydrocarbons
(only C and H)|

* Alkyl
* Methyl
* Ethyl
* Propyl
* Cyclopropyl
* Butyl
* Pentyl
* Methylene
* Bridge
* Methine
* Alkene
* Vinyl
* Allyl
* 1-Propenyl
* Crotyl
* Allene
* Cumulene
* Aryl
* Phenyl
* Benzyl
* Alkyne
* Carbene

Only carbon,
hydrogen,
and oxygen
(only C, H and O)|

| R-O-R|

* Acetal
* Alcohol
* Alkoxy
* Methoxy
* Ether
* Enol ether
* Epoxide
* Peroxy
* Hydroperoxy
* Dioxiranes
* Ethylenedioxy
* Methylenedioxy

|

carbonyl|

* Acyl
* Acetyl
* Acryloyl
* Benzoyl
* Aldehyde
* Ketene
* Ketone
* Ynone
* Reductone

carboxy|

* Carboxyl
* Acetoxy
* Anhydride
* Ester
* Orthoester

Only one
element,
not being
carbon,
hydrogen,
or oxygen
(one element,
not C, H or O)|

| Nitrogen|

* Amine
* Enamine
* Ammonium
* Hydrazo
* Nitrene
* Imine
* Oxime
* Hydrazone
* Azo
* Amide
* Imidate
* Amidine
* Carbamate
* Imide
* Nitrile
* Isonitrile
* Cyanate
* Isocyanate
* Nitrate
* Nitrite
* Nitro
* Nitroso
* NONOate
* Triazole
* Tetrazole

|

Silicon|

* Silane
* Hydrosilane
* Chlorosilane
* Silene
* Silanol
* Siloxide
* Siloxane
* Silanone
* Silether
* Silole
* Silatrane
* Silicate

Phosphorus|

* Phosphate
* Phosphodiester
* Phosphonate
* Phosphite
* Phosphonous
* Phosphinate
* Phosphine oxide
* Phosphine
* Phosphonium
* Phosphaalkene
* Phosphaalkyne
* Phosphaallene

Sulfur|

* Thiol
* Thioether
* Sulfonium
* Thia-crown ether
* Persulfide
* Disulfide
* Sulfenic acid
* Thiosulfinate
* Sulfoxide
* Thiosulfonate
* Sulfinic acid
* Sulfone
* Sulfonic acid
* Thioketone
* Thial
* Thioester
* Thionoester
* Thioxanthate
* Xanthate

Boron|

* Boronic acid
* Borinic acid

Selenium|

* Selenol
* Selenonic acid
* Seleninic acid
* Selenenic acid
* Selone
* Selenoether

Tellurium|

* Tellurol
* Telluroketone
* telluroether

Polonium|

* Polonol
* Polonoether

Halo|

* Haloalkane
* Fluoroethyl
* Trifluoromethyl
* Trichloromethyl
* Trifluoromethoxy
* Hypervalent iodine
* Vinyl halide
* Iodide
* Acyl halide
* Chloride
* Perchlorate

Other|

* Isothiocyanate
* Phosphoramides
* Sulfenyl chloride
* Sulfonamide
* Thiocyanate
* Sulfinylamines

See also
chemical classification
chemical nomenclature

inorganic
organic
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