''trans''-Cyclooctene is a

cyclic Cycle, cycles, or cyclic may refer to: Anthropology and social sciences * Cyclic history, a theory of history * Cyclical theory, a theory of American political history associated with Arthur Schlesinger, Sr. * Social cycle, various cycles in s ...

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

with the formula ��(CH₂)₆CH=CH– where the two C–C single bonds adjacent to the double bond are on opposite sides of the latter's plane. It is a colorless liquid with a disagreeable odor.

Cyclooctene Cyclooctene is the cycloalkene with a formula . Its molecule has a ring of 8 carbon atoms, connected by seven single bonds and one double bond. Cyclooctene is notable because it is the smallest cycloalkene that can exist stably as either the cis� ...

is notable as the smallest cycloalkene that is readily isolated as its ''trans''-

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

. The ''cis''-isomer is much more stable; the ring-strain energies being 16.7 and 7.4 kcal/mol, respectively.Ron Walker, Rosemary M. Conrad, and Robert H. Grubbs (2009): "The living ROMP of ''trans''-cyclooctene". ''Macromolecules'', volume 42, issue 3, pages 599–605. A planar arrangement of the ring carbons would be too strained, and therefore the stable conformations of the ''trans'' form have a bent (non-planar) ring. Computations indicate that the most stable "crown" conformation has the carbon atoms alternately above and below the plane of the ring. A "half-chair" conformation, with about 6 kcal/mol higher energy, has carbons 2,3,5,6, and 8 on the same side of the plane of carbons 1,4, and 7. All conformations of ''trans''-cyclooctene are

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

(specifically, what some call planar-chiral) and the

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

s can be separated.Arthur C. Cope, C. R. Ganellin, H. W. Johnson, T. V. Van Auken, and Hans J. S. Winkler (193): "Molecular asymmetry of olefins. I. Resolution of ''trans''-cyclooctene". ''Journal of the American Chemical Association'', volume 85, issue 20, pages 3276–3279. Arthur C. Cope and Anil S. Mehta (1964): "Molecular asymmetry of olefins. II. The absolute configuration of ''trans''-cyclooctene". ''Journal of the American Chemical Association'', volume 86, issue 24, pages 5626–5630. In theory, conversion of between the enantiomers can be done, without breaking any bonds, by twisting the whole –CH=CH– group, rigidly, by 180 degrees. However, that entails passing one of its hydrogens through the crowded ring.

Preparation

''trans''-Cyclooctene was first synthesized on a preparatory scale by

Arthur C. Cope Arthur C. Cope (June 27, 1909 – June 4, 1966) was an American organic chemist and member of the United States National Academy of Sciences. He is credited with the development of several important chemical reactions which bear his name includin ...

with a

Hofmann elimination Hofmann elimination is an elimination reaction of an amine to form alkenes. The least stable alkene (the one with the least number of substituents on the carbons of the double bond), called the Hofmann product, is formed. This tendency, known as ...

reaction of iodide. The reaction gives a mixture of ''cis'' and ''trans'' isomers, and the ''trans'' isomer is selectively trapped as a

complex Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...

with

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...

. Other methods exist where the ''trans'' isomer is synthesized from the ''cis'' isomer in several synthetic steps. For instance, it can be prepared in almost 100% yield by converting the ''cis'' isomer to

1,2-epoxycyclooctane Onekama ( ) is a village in Manistee County in the U.S. state of Michigan. The population was 411 at the 2010 census. The village is located on the shores of Portage Lake and is surrounded by Onekama Township. The town's name is derived from "On ...

("cyclooctene oxide") followed by reactions with

lithium diphenylphosphide Lithium diphenylphosphide contains lithium and the organophosphorus anion with the formula (C6H5)2PLi. It is an air-sensitive solid that is used in the preparation of diphenylphosphino compounds. As an ether complex, the lithium salt is dark red ...

() and with methyl iodide . (Similar procedures can give ' isomers of 1,4-cyclooctadiene and

1,5-cyclooctadiene Cycloocta-1,5-diene is a cyclic hydrocarbon with the chemical formula , specifically . There are three configurational isomers with this structure, that differ by the arrangement of the four C–C single bonds adjacent to the double bonds. Each ...

).Edwin Vedejs, Karel A. J. Snoble, and Philip L. Fuchs (1973): "Phosphorus betaines derived from cycloheptene and cyclooctene oxides. Inversion of cyclooctenes". ''Journal of Organic Chemistry'', volume 38, issue 6, pages 1178–1183. In addition, a

photochemical Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–7 ...

method exists for the direct ''cis''–''trans'' isomerisation. Although this equilibrium strongly favours the more stable ''cis'' form, the reaction can be driven towards the ''trans'' form by trapping with silver ions.John S. Swenton (1969): "Photoisomerization of ''cis''-cyclooctene to ''trans''-cyclooctene". ''Journal of Organic Chemistry'', volume 34, issue 10, pages 3217–3218.

Reactions

Because of the higher internal strain on the double bond, the ''trans'' isomer is more reactive than the ''cis'' isomer and of typical unsaturated hydrocarbons. For instance, its double bond will rapidly

add Addition (usually signified by the plus symbol ) is one of the four basic operations of arithmetic, the other three being subtraction, multiplication and division. The addition of two whole numbers results in the total amount or '' sum'' of ...

tetrazine Tetrazine is a compound that consists of a six-membered aromatic ring containing four nitrogen atoms with the molecular formula C2 H2 N4. The name ''tetrazine'' is used in the nomenclature of derivatives of this compound. Three core-ring isome ...

and its derivatives.Ramajeyam Selvaraj, Joseph M Fox "''trans''-Cyclooctene — a stable, voracious dienophile for bioorthogonal labeling". ''Current Opinion in Chemical Biology'', volume 17, issue 5, pages 753-760 The compound also readily polymerizes with a

ruthenium Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemical ...

-based initiator.

References

{{Authority control Cycloalkenes Foul-smelling chemicals