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Alkenes acid-base chemistry

Chapters 1—10 begin a study of organic compounds by first reviewing the fundamentals of covalent bonding, the shapes of molecules, and acid-base chemistry. The structures and typical reactions of several important classes of organic compounds are then discussed alkanes, alkenes and alkynes, haloalkanes, alcohols and ethers, benzene and its derivatives, and amines, aldehydes, and ketones, and finally carboxylic acids and their derivatives. [Pg.837]

This chapter will build on principles introduced in previous chapters and show applications to common chemical reactions of two important hydrocarbon functional groups alkenes and alkynes. The chapter will also introduce several new chemical reagents (compounds that react with an alkene or alkyne to give a new molecule), as well as several new types of reactions. The theme of acid-base chemistry will be used as a basis for understanding each chemical transformation where it is appropriate. Mechanisms that are the step-by-step processes by which one molecule is transformed into another by tracking the intermediates will also be discussed. The concept of mechanism was introduced in Chapter 7 (Section 7.8). [Pg.416]

Chapter 10 introduces the acid-base chemistry of molecules that contain the C=C and C C functional groups. Related reactions that do not fall under the acid-base category are also presented. Chapter 11 uses nucleophiles, which are loosely categorized as specialized Lewis bases, in reactions with alkyl halides. These are substitution reactions. Chapter 12 shows the acid-base reaction of alkyl halides that leads to alkenes (an elimination reaction), and Chapter 13 ties Chapters 11 and 12 together with a series of simplifying assumptions that allows one to make predictions concerning the major product. [Pg.1494]

The chemistry of Lewis acids is quite varied, and equilibria such as those shown in Eqs. (28) and (29) should often be supplemented with additional possibilities. Some Lewis acids form dimers that have very different reactivities than those of the monomeric acids. For example, the dimer of titanium chloride is much more reactive than monomeric TiCL (cf., Chapter 2). Alkyl aluminum halides also dimerize in solution, whereas boron and tin halides are monomeric. Tin tetrachloride can complex up to two chloride ligands to form SnCL2-. Therefore, SnCl5 can also act as a Lewis acid, although it is weaker than SnCl4 [148]. Transition metal halides based on tungsten, vanadium, iron, and titanium may coordinate alkenes, and therefore initiate polymerization by either a coordinative or cationic mechanism. Other Lewis acids add to alkenes this may be slow as in haloboration and iodine addition, or faster as with antimony penta-chloride. [Pg.177]

Several reactions of alkenes are discussed in Chapter 10 that involve an acid-base reaction in which the alkene is a Brpnsted-Lowry base or a Lewis base. In that chapter, two other reactions transformed an alkene into a vicinal diol or into an epoxide. Both of these reactions are oxidations, although they were discussed in a different context at that time. This section will review the previously discussed chemistry to put it into proper perspective as oxidation reactions. [Pg.822]

Conjugated dienes and conjugated carbonyl compounds were discussed as more or less separate entities in the previous chapter. This chapter will show that one may react with the other. 1,3-Dienes react with alkenes, particularly with the C=C unit of a conjugated carbonyl compound, to form cyclohexene derivatives. This is a [4-1-2] cycloaddition, commonly known as the Diels-Alder reaction. The mechanism for this reaction requires an examination of the molecular orbitals of the reactants. This is one of the most important reactions in organic chemistry. It is also important to note that this reaction is not an acid-base reaction it is a new type of reaction and a new type of mechanism. The product is often a difunctional molecule. [Pg.1241]

In addition to the iminium-salt-based chemistry and to cross-coupling processes, aqueous formaldehyde can also be used as the carbonylated substrate in the Prins reaction, an intermolecular ene-type acid-catalyzed reaction with alkenes providing 1,3-dioxanes (Adams and Bhatnagar, 1977). [Pg.130]

With the renaissance in alkene chemistry engendered by the rising versatility of olefin metathesis in both fine chemical and commodity production, new methods for alkene isomerization are of increasing interest and importance. Alkene isomerization can be performed using Bronsted-Lowry acid or base catalysis (1). However, these reactions are limited to substrates which tolerate carbanionic or carbocation intermediates, and are susceptible to undesired side reactions. [Pg.379]

With a common intermediate from the Medicinal Chemistry synthesis now in hand in enantiomerically upgraded form, optimization of the conversion to the amine was addressed, with particular emphasis on safety evaluation of the azide displacement step (Scheme 9.7). Hence, alcohol 6 was reacted with methanesul-fonyl chloride in the presence of triethylamine to afford a 95% yield of the desired mesylate as an oil. Displacement of the mesylate using sodium azide in DMF afforded azide 7 in around 85% assay yield. However, a major by-product of the reaction was found to be alkene 17, formed from an elimination pathway with concomitant formation of the hazardous hydrazoic acid. To evaluate this potential safety hazard for process scale-up, online FTIR was used to monitor the presence of hydrazoic acid in the head-space, confirming that this was indeed formed during the reaction [7]. It was also observed that the amount of hydrazoic acid in the headspace could be completely suppressed by the addition of an organic base such as diisopropylethylamine to the reaction, with the use of inorganic bases such as... [Pg.247]

A very recent addition to the already powerful spectrum of microwave Heck chemistry has been the development of a general procedure for carrying out oxidative Heck couplings, that is, the palladium)11)-catalyzed carbon-carbon coupling of arylboronic acids with alkenes using copper(II) acetate as a reoxidant [25], In a 2003 publication (Scheme 6.6), Larhed and coworkers utilized lithium acetate as a base and the polar and aprotic N,N-dimethylformamide as solvent. The coupling... [Pg.111]

Further chemistry of alkenes and alkynes is described in this chapter, with emphasis on addition reactions that lead to reduction and oxidation of carbon-carbon multiple bonds. First we explain what is meant by the terms reduction and oxidation as applied to carbon compounds. Then we emphasize hydrogenation, which is reduction through addition of hydrogen, and oxidative addition reactions with reagents such as ozone, peroxides, permanganate, and osmium tetroxide. We conclude with a section on the special nature of 1-alkynes— their acidic behavior and how the conjugate bases of alkynes can be used in synthesis to form carbon-carbon bonds. [Pg.405]

The initial coordination of reactants has indeed been proposed to explain the selective oxidation of alkenes in the presence of saturated hydrocarbons. It was argued that, owing to the hydrophobic nature of titanium silicates, the concentration of both hydrocarbons inside the catalyst pores is relatively high and hence the alkenes must coordinate to TiIv. Consequently, the titanium peroxo complex will be formed almost exclusively on Tilv centers that already have an alkene in their coordination sphere, and will therefore oxidize this alkene rather than an alkane which may be present in the catalyst (Huybrechts et al., 1992). Objections to this proposal are based on the fact that the intrinsically higher reactivity of alkenes with respect to saturated hydrocarbons is sufficient to account for the selectivity observed (Clerici et al., 1992). But coordination around the titanium center of an alcohol molecule, particularly methanol, is nevertheless proposed to explain the formation of acidic species, as was previously discussed. In summary, coordination around Tiiv could play a more important role than it does in solution chemistry as a consequence of the hydrophobicity of the environment where the reactions take place. [Pg.325]


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