Naming alkenes

We have already discussed one important chemical property of alkynes the acidity of acetylene and terminal alkynes In the remaining sections of this chapter several other reactions of alkynes will be explored Most of them will be similar to reactions of alkenes Like alkenes alkynes undergo addition reactions We 11 begin with a reaction familiar to us from our study of alkenes namely catalytic hydrogenation... 

The sex attractant given off by the common housefly is an alkene named muscahtre. Propose a synthesis of muscalure starting from acetylene and any alkyl halides needed. What is the IUPAC name for muscalure ... 

Enantiotopic (NMR), 455 Endergonic. 153 Endergonic reaction, Hammond postulate and, 197-198 Endo stereochemistry, Diels-Alder reaction and, 495 Endothermic, 154 -ene, alkene name ending, 176 Energy difference, equilibrium position and, 122... 

In our study of the simple hydrocarbons, there are only two functional groups. One is a carbon-to-carbon double bond. Hydrocarbons that contain a carbon-to-carbon double bond are called alkenes. Naming alkenes is very similar to naming alkanes. The major difference is that the carbon base has an -ene ending instead of the -ane ending. The carbon backbone of the base hydrocarbon is numbered so the position of the double bond has the lowest location number. 

The characteristic features of hydroboration of alkenes—namely, regioselec-tivity, stereoselectivity, syn addition, and lack of rearrangement—led to the postulation of a concerted [2 + 2] cycloaddition of borane353,354 via four-center transition state 37. Kinetic studies, solvent effects, and molecular-orbital calculations are consistent with this model. As four-center transition states are unfavorable, however, the initial interaction of borane [or mentioned monobridged dimer, Eq. (6.56)] with the alkene probably involves an initial two-electron, three-center interaction355,356(38, 39). 

In the second part of the reaction of Figure 12.24, the a-palladated cyclohexanone E decomposes (since it is an alkylpalladium(II) compound with a syn-H atom in the position /3 to the metal) to an alkene, namely the previously mentioned unsaturated ketone B, and to H-Pd-Cl. In Chapter 16 this type of reaction will be repeatedly encountered in connection with the keyword /3-hydride elimination as A —> B in the Figures 16.13 and 16.14 and as step 7 of Figure 16.35 (part II). H-Pd-Cl decomposes according to the equation H-Pd-C1 —> Pd(0) + HC1, which describes a reductive elimination. Reductive eliminations will be... 

The photo-SNl reaction with particular classes of alkenes - namely enamines, silyl enol ethers and silyl ketene acetals - affords a smooth synthesis of a-aryl ketones,... 

Alkenes are hydrocarbons that contain carbon-carbon double bonds. A carbon-carbon double bond is the most reactive part of an alkene, so we say that the double bond is the functional group of the alkene. Alkene names end in the -ene suffix. If the double bond might be in more than one position, then the chain is numbered and the lower number of the two double-bonded carbons is added to the name to indicate the position of the double bond. 

Alkenes as Substituents Alkenes named as substituents are called alkenyl groups. They can be named systematically (ethenyl, propenyl, etc.), or by common names. Common alkenyl substituents are the vinyl, allyl, methylene, and phenyl groups. The phenyl group (Ph) is different from the others because it is aromatic (see Chapter 16) and does not undergo the typical reactions of alkenes. 

There are four main general methods [40 2] for the preparation of perfluorinated alkenes, namely dehydrohalogenation, dehalogenation, pyrolysis and halogen exchange reactions of appropriate fluorinated precursors. The overall features of the mechanisms of each of these processes have already been discussed (Chapters 6 and 7, Sections 1 and 11). Representative examples of each of these types of synthesis are collated in Table 7.5 clearly the method of choice for the synthesis of a particular fluoroalkene will depend... 

Count the munber of carbons in the longest continuous chain that contains the double bond, and assign the appropriate alkene name. 

Write the number corresponding to the first carbon in the double bond, followed by a hyphen and then the alkene name. 

Write an equation showing the hydration of each of the following alkenes. Name each of the products using the I.U.P.A.C. Nomenclature System. 

Alkene names differ from those of alkanes in two respects ... 

Most alkene names need a number to indicate the position of the double bond. (The four names above do not, because there is no ambiguity.) The lUPAC rules you learned in Chapter 2 apply to alkenes as well ... 

The mechanisms of dehalogenations have been reviewed by Miller and in a series of papers , the stereoselectivity of the dehalogenation of the stilbene dibromides with a wide variety of reagents has been discussed. The meso-stilbene dibromide always eliminates to give the thermodynamically more stable alkene, namely tra 5-stilbene which is product of apparent a t/-elimina-tion. However, the J/-stilbene dibromide gives both cis- and rm i-stilbenes, and the ratio of these products can provide useful mechanistic information. One-electron reductants, such as chromous ion, give rise to intermediate radical formation in which rotation about the Ca-Cg bond allows thermodynamic control of the reaction. Two-electron reductants, such as iodide ion in dimethyl formamide, induce highly stereoselective a i-elimination. In protic solvents, carbonium ion intermediates were proposed to explain the trend towards thermodynamic control. Miller has proposed a reaction mechanism which embraces elimination, substitution, and electrophilic addition to alkenes. 

The nomenclature of FA reflects the long history of their smdy and description. Most FA were originally described under trivial names prior to the adoption of the international molecular nomenclature rules in 1892 (Table 3.1). Even after adopting the International Union of Pure and Applied Chemistry (lUPAC) system for nomenclature (lUPAC-IUB, 1977), the habit of assigning trivial names to FA continues. The basis of the systematic nomenclature system is an extension of that accepted for hydrocarbon (alkane/alkene) naming. Hence, the descriptive name is based on the number of carbon atoms contained in the molecule, with the suffix -e replaced with -oic acid. However, in most instances, FA are referred to by their formula notations. As is the case with systematic and trivial names, there exists an lUPAC accepted formula notation nomenclature and several earher versions (Table 3.2). Each system... 

Compounds containing double or triple bonds between carbon atoms are said to be unsaturated. The alkenes contain double bonds, alkynes contain triple bonds, and aromatics contain a six-membered ring with three double bonds, objectiva 1, Exercise 2.2. In the lUPAC nomenclature system, alkene names end in -ene, and alkynes end in -yne. 

An early report on a nickel-catalysed Mizoroki-Heck-type arylalion of an alkene was disclosed by Chiusoli et al. [28] while studying syntheses of linear, deconjugated unsaturated acids (Scheme 10.7). However, in this report, only one particular alkene, namely potassium salt 20, was employed. This substrate is supposed to promote the Mizoroki-Heck-type arylation through precoordination to the transition metal catalyst. From a mechanistic viewpoint it is interesting to note that the nickel catalyst did not require the use of a stoichiometric, relatively strong reducing agent (see below). 

In contrast to fats and phospholipids, terpenes and steroids cannot be hydrolyzed to simpler units. However, Otto Wallach in the nineteenth century and Leopold Ruzicka (Croatian Nobel laureate) in the first half of twentieth century discovered that these compounds can be decomposed into simpler structures that consist of five carbon atoms. These units are structural analogs of the alkene named isoprene (2-methylbuta-1,3-diene). Isoprene can be regarded as a molecule containing a head and a tail. 

In methanol, pseudo-second-order kinetics are observed when a high concentration of Br is present. Under these conditions, the dominant contribution to the overall rate comes from the third term of the general expression. The occurrence of third-order terms suggests the possibility of a mechanism similar to the Ad S mechanism for addition of hydrogen halides to alkenes, namely, attack of halide ion on an alkene-halogen complex. 

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