Cumulative double bonds

There is, however, other evidence that speaks for the bromonium ion concept and against competition between AdE2 and Ad3 pathways.35 We have already noted that, in polar solvents, addition of bromine to multiple bonds is first-order in bromine when bromine is present in low concentration. Moreover, as Table 7.7 shows, increasing the number of substituents on the double bond cumulatively increases the rate of bromination of nonconjugated olefins in polar solvents irrespective of whether each new substituent is on the same or on the other olefinic carbon as the last.36 Dubois has found that the bimolecular rate constants for addition of bromine to alkyl substituted ethylenes are correlated by... 

Dienes are very important monomers. The molecule of any diene may carry various substituents. In spite of the great number of possible variants, fewer are employed in production and science than in the case of vinyl monomers. The mutual position of double bonds, cumulative, conjugated or isolated, is of great importance. 

CH = C = CH— are called allenes after the simplest member of the series. They are said to have cumulated double bonds. They react in most cases normally, that is, each double bond is unaffected by the proximity of the other they are converted by heating into the isomeric acetylenes. Compounds of the type... 

Cumulated dienes are those m which one carbon atom is common to two carbon-carbon double bonds The simplest cumulated diene is 1 2 propadiene also called allene and compounds of this class are generally referred to as allenes... 

Which IS the most stable arrangement of double bonds m an alkadiene—isolated con jugated or cumulated ... 

The cumulated double bonds of an allenic system are of relatively high energy The heat of hydrogenation of allene is more than twice that of propene... 

Elimination is typically regioselective and gives a conjugated diene rather than an isolated or cumulated diene system of double bonds... 

Critical micelle concentration (Section 19 5) Concentration above which substances such as salts of fatty acids aggre gate to form micelles in aqueous solution Crown ether (Section 16 4) A cyclic polyether that via lon-dipole attractive forces forms stable complexes with metal 10ns Such complexes along with their accompany mg anion are soluble in nonpolar solvents C terminus (Section 27 7) The amino acid at the end of a pep tide or protein chain that has its carboxyl group intact—that IS in which the carboxyl group is not part of a peptide bond Cumulated diene (Section 10 5) Diene of the type C=C=C in which a single carbon atom participates in double bonds with two others... 

Conjugated with a carbon-carbon double bond —C=C—C=C— Conjugated with a carbon-oxygen double bond —C=C—C=0 Cumulative —C=C=C— or —C=C=0 Triple bond... 

Cumulative carbon-carbon-oxygen double bonds H—C—C=C=0 108(1)... 

Table 7.20 Absorption Frequencies of Single Bonds to Hydrogen Table 7.21 Absorption Frequencies of Triple Bonds Table 7.22 Absorption Frequencies of Cumulated Double Bonds Table 7.23 Absorption Frequencies of Carbonyl Bands...

Table 7.32 Raman Frequencies of Cumulated Double Bonds...

Ketenes are oxo compounds with cumulated carbonyl and carbon—carbon double bonds of the general stmcture R R2C—C—O, where and R2 may be any combination of hydrogen, alkyl, aryl, acyl, halogen, and many other functional groups. Ketenes with R = sometimes called aldoketenes,... 

Ketenes and related compounds have been reviewed extensively (1 9). For the synthesis and synthetic uses of conjugated ketenes see Reference 10. Ketenes with three or more cumulated double bonds have been prepared (11,12). The best known is carbon suboxide [504-64-3] 3 2 preparative uses and has been reviewed (13—16). Thioketenes (17,18), ketenimines (19—21), and their dimers show interesting reactivity, but they have not achieved iadustrial importance to date. 

Aldehydes, ketones and cumulated double bonds react with oxiranes to form five-membered heterocycles (e.g. Schemes 31 and 32) (64HC(19-1)453). 

The two most commonly applied systems for naming polycyclic parents are in some ways complementary. Fusion nomenclature provides names for structures containing the maximum number of non-cumulative double bonds von Baeyer nomenclature (Section 1.02.3.4) names fully saturated structures. Thus names for partially hydrogenated structures can be arrived at either by adding hydro prefixes to fusion names or ene , diene , etc. suffixes to von Baeyer names (see examples 29 and 30). If needed, rules are available for... 

The prefixes to be attached to the name of the base component are formed by changing the terminal e of the trivial or Hantzsch-Widman names of the components (in the form containing the maximum number of non-cumulative double bonds) into o . Some prefixes are further abbreviated, as exemplified in the following list ... 

The following prefixes are used to represent monocyclic hydrocarbon components other than benzene cyclopropa-, cyclobuta-, cyclopenta-, cyclohepta-, etc. When a monocyclic hydrocarbon is the base component, it carries the ending ene , signifying the maximum number of non-cumulative double bonds (examples 33 and 34). 

Most parent structures consist essentially of an assembly of rings and/or chains, the degree of hydrogenation of which is defined (usually completely saturated or containing the maximum number of non-cumulative double bonds in cyclic portions), and having no attached functional substituents (the carbohydrates are a notable exception to this). The stereochemistry at all (or most) chiral centres is defined thus such parent structures are sometimes referred to as stereoparents . Some examples are shown (77)-(83). 

The 1,3-dipolar cycloadditions offluonnatedallenes provide a rich and varied chemistry Allenes, such as 1,1-difluoroallene and fluoroallene, that have fluorine substitution on only one of their two cumulated double bonds are very reactive toward 1,3-dipoles Such activation derives from the electron attracting inductive and hyperconjugative effects of the allylic fluorine substituent(s) that give nse to a considerable lowering of the energy of the LUMO of the C(2)-C(3) n bond [27]... 

A hydrocarbon that contains two double bonds is called an alkadiene, and the relationship between the double bonds may be described as isolated, conjugated, or cumulated. Isolated diene units are those in which two carbon-carbon double bond units are separated from each other by one or more 5/r -hybridized carbon atoms. 1,4-Pentadiene and 1,5-cyclooctadiene have isolated double bonds ... 

Which is the most stable aiiangement of double bonds in an alkadiene—isolated, conjugated, or cumulated ... 

Section 10.5 Dienes aie classified as having isolated, conjugated, or cumulated double bonds. 

Cumulated diene (Section 10.5) Diene of the type C=C=C, in which a single carbon atom participates in double bonds with two others. 

Double bonds that occur together in a straight chain are. said to be cumulated. Examples are... 

This fundamental discovery dramatically affected the whole chemistry of main-group elements. Subsequently, a series of new compounds with silicon element multiple bonds has been introduced. Within only a few years, stable silenes (silaethenes with a Si = C double bond) [8-11], silaimines Si = N [12-14], and silaphosphenes Si = P [15] were synthesized. As a pacemaker, silicon chemistry has exerted a strong influence on further areas of main-group chemistry a variety of stable molecules with Ge = Ge [16], P = P [17], As = As [18], P = C and P = C [19-22] bonds were subsequently isolated, and systems with cumulated double bonds P = C = P [23-25] are also known today. 

These carbene (or alkylidene) complexes are used for various transformations. Known reactions of these complexes are (a) alkene metathesis, (b) alkene cyclopropanation, (c) carbonyl alkenation, (d) insertion into C-H, N-H and O-H bonds, (e) ylide formation and (f) dimerization. The reactivity of these complexes can be tuned by varying the metal, oxidation state or ligands. Nowadays carbene complexes with cumulated double bonds have also been synthesized and investigated [45-49] as well as carbene cluster compounds, which will not be discussed here [50]. 

Triple bonds and cumulative double bonds 2-Carb-18. Branched-chain sugars... 

Monosaccharide derivatives having a triple bond or cumulative double bonds in the backbone chain are named by the methods of 2-Carb-17.2, with the infix n-yn for a triple bond and infixes such as ij-dien for cumulative double bonds. 

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