Caran

Structural formula
	Structure without showing the stereochemical configuration
General
Surname	Caran
other names	Karan; 3,7,7-trimethylbicyclo [4.1.0] heptane;
Molecular formula	C 10 H 18
Brief description	colorless, pleasant smelling liquid
External identifiers / databases
PubChem	79043
Wikidata	Q27116560
properties
Molar mass	138.25 g mol −1
Physical state	liquid
density	0.841 g cm −3
boiling point	169 ° C
safety instructions
GHS hazard labeling ; no classification available
GHS hazard labeling ; no classification available
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Caran is a bicyclic, bridged hydrocarbon that forms the backbone for a group of terpenes . With the empirical formula C ₁₀ H ₁₈ , it is a monoterpene , i.e. a constitutional isomer of Bornane and Pinane .

structure

Carane and the terpenes derived from it can also be understood as derivatives of the hydrocarbon bicyclo [4.1.0] heptane. This parent compound consists of a six-membered ring (cyclohexane ring) and a three-membered ring (cyclopropane ring), which are cis -linked ( fused ). The carbon atoms of the six-membered ring are not in one plane. In the caran there are still two geminal methyl groups on carbon atom 7 and one methyl group on C-3. If the carbon atoms of the six-membered ring are projected into a plane, the C-3-methyl (= C-10) can be on the same side as C-7 (of the three-membered ring), or on the opposite side. Therefore, two isomers ( diastereomers ) of the bicyclic hydrocarbon are possible, which were referred to as cis -caran and trans -caran, respectively. Both isomers are chiral.

Isomers of caran
Surname	cis caran	trans -Caran
other names	cis -3,7,7-trimethylbicyclo [4.1.0] heptane (1 R , 3 R , 6 S ) -3,7,7-trimethylbicyclo [4.1.0] heptane	trans -3,7,7-trimethylbicyclo [4.1.0] heptane (1 R , 3 S , 6 S ) -3,7,7-trimethylbicyclo [4.1.0] heptane
Structural formula
CAS number	18968-24-6 2778-68-9 (-) - cis	18968-23-5 (+) - trans
CAS number	554-59-6 (unspec.)
PubChem	12302437	12302439
PubChem	79043 (unspec.)
Refractive index	1.4550 at 20 ° C	1.4565 at 20 ° C
Optical activity [α] _D²⁰	−37.7 °	+ 63.5 °

Occurrence and manufacture

3-carene

The hydrocarbons do not seem to occur in nature, but the unsaturated hydrocarbon 3-carene as a component of turpentine oils, as well as some alcohols and ketones .

A synthesis of cis -caran starts from 3-carene, which after hydroboration and oxidation gave the alcohol cis -caran- trans -4-ol. This was deoxygenated by reducing its tosylate with lithium aluminum hydride.

trans -caran was obtained from caran-2-one by Wolff-Kishner reduction . However, the ketone is not a natural substance , but was produced synthetically.

The simplest method to produce these bicyclic hydrocarbons should be the hydrogenation of 3-carene. However, it is not selective. A previous isomerization (equilibration) to 2-carene was observed in the case of the heterogeneous catalytic hydrogenation. In the end, cis -carane is formed in addition to 1,1,4-trimethylcycloheptane, i.e. H. the C-1 / C-6 bond is partially split hydrogenolytically. In heterogeneous catalytic hydrogenation with platinum black , for example, a mixture of cis -caran (65%), trans -caran (32.5%) and 1,1,4-trimethylcycloheptane (2.5%) is to be formed. Pure cis and trans caran can be obtained by fractional distillation of the mixture .

literature

D. Whittaker: The Monoterpenes in: AA Newman (Ed.): Chemistry of Terpenes and Terpenoids . P. 35, Academic Press, London 1972, ISBN 0-12-517950-2

Individual evidence

↑ ^a ^b ^c Entry on Caran. In: Römpp Online . Georg Thieme Verlag, accessed on October 31, 2012.
↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
↑ John Lionel Simonsen: The Terpenes Volume II The Dicyclic Terpenes, Sesquiterpenes and their ... University Press, 1947, pp. 54 ( limited preview in Google Book search).
^ ^A ^b ^c ^d ^e ^f W. Cocker, PVR Shannon and PA Staniland: The chemistry of terpenes. Part II. The physical properties of some cis - trans substituted cyclohexanes . J. Chem. Soc. C, 1966, 946-949, doi : 10.1039 / J39660000946 .
↑ Wesley Cocker, PVR Shannon, PA Staniland: The chemistry of terpenes. Part I. Hydrogenation of the pinenes and the carenes , J. Chem. Soc. C, 1966, 41-47, doi : 10.1039 / J39660000041 .
↑ II Bardychev, EF Buinova, AL Pertsovskii: Synthesis and study of the properties of cis and trans caranes , Vesti Acad. Navuk Belarus. SSR Ser. Khim. Navuk, 1970, 99-101. Quoted from Chemical Abstracts , Vol 74 (1971), Paper No. 112223j ( 74 : 112223j).

[roempp-1] Entry on Caran. In: Römpp Online . Georg Thieme Verlag, accessed on October 31, 2012.

[NV-2] This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.

[John_Lionel_Simonsen-3] John Lionel Simonsen: The Terpenes Volume II The Dicyclic Terpenes, Sesquiterpenes and their ... University Press, 1947, pp. 54 ( limited preview in Google Book search).

[cocker-4] A ^b ^c ^d ^e ^f W. Cocker, PVR Shannon and PA Staniland: The chemistry of terpenes. Part II. The physical properties of some cis - trans substituted cyclohexanes . J. Chem. Soc. C, 1966, 946-949, doi : 10.1039 / J39660000946 .

[5] Wesley Cocker, PVR Shannon, PA Staniland: The chemistry of terpenes. Part I. Hydrogenation of the pinenes and the carenes , J. Chem. Soc. C, 1966, 41-47, doi : 10.1039 / J39660000041 .

[6] II Bardychev, EF Buinova, AL Pertsovskii: Synthesis and study of the properties of cis and trans caranes , Vesti Acad. Navuk Belarus. SSR Ser. Khim. Navuk, 1970, 99-101. Quoted from Chemical Abstracts , Vol 74 (1971), Paper No. 112223j ( 74 : 112223j).