Reactions with Saturated Aliphatic Compounds

The reaction of OH with saturated aliphatic compounds is known to take place mainly by hydrogen abstraction from the alkyl groups. For example, amines undergo a reaction such as (32). However,... 

Nucleophilic substitution (5 ) reactions of saturated aliphatic compounds may be either associative or dissociative and the majority lie between the limits set by iSnI reactions, in which the rate-determining step is heterolysis of the bond to the leaving group, and typical 5 2 reactions with fully synchronous bond-formation and bond-rupture. Nl-like reactions represent an intermediate case and are characterized by a greater extent of bond-rupture than bond-formation. Hence, in aliphatic 5 reactions the rate-limiting process involves some degree of prior or concurrent bond-rupture. 

Sulfur trioxide and its hydrates are generally unsuitable for sulfonating saturated aliphatic compounds. Either no reaction occurs, or oxidative decomposition takes place, yielding a complex mixture. Long-chain saturated fatty acids can, however, be smoothly sulfonated with SO3 (liquid or vapor) to give good yields of a-sulfo acids as follows ... 

With saturated carbonyl compounds, and especially with aromatic carbonyl compounds, reaction between the photoexcited carbonyl chromophore and alkenes results in the formation of four-membered cyclic ethers (oxetanes). The addition of carbonyl compounds to alkenes to give oxetanes is often referred to as the Paterno-Buchi reactionf" The reaction is stereospecific for at least some aliphatic... 

In the Diels-Alder reaction with inverse electron demand, the overlap of the LUMO of the 1-oxa-l,3-butadiene with the HOMO of the dienophile is dominant. Since the electron-withdrawing group at the oxabutadiene at the 3-position lowers its LUMO dramatically, the cycloaddition as well as the condensation usually take place at room or slightly elevated temperature. There is actually no restriction for the aldehydes. Thus, aromatic, heteroaromatic, saturated aliphatic and unsaturated aliphatic aldehydes may be used. For example, a-oxocarbocylic esters or 1,2-dike-tones for instance have been employed as ketones. Furthermore, 1,3-dicarbonyl compounds cyclic and acyclic substances such as Meldmm s acid, barbituric acid and derivates, coumarins, any type of cycloalkane-1,3-dione, (1-ketoesters, and 1,3-diones as well as their phosphorus, nitrogen and sulfur analogues, can also be ap-... 

This chapter is concerned almost exclusively with the chemistry of saturated aliphatic monohydric alcohols with particular emphasis on the reactions used in the conversion of these alcohols to other useful compounds. Manufacture of many of the alcohols is covered in other chapters. 

Thus one might expect nucleophilic displacements on —COX compounds with azide ion to be intermediate in character between saturated aliphatic 5 n2 and S Ar reactions. However, while there are numerous examples of the formation of azides by displacement of X from —COX compounds with azide ion, there appear to be no important mechanistic studies on such reactions. 

In aliphatic heterocyclic compounds, the nitrogen atom is part of a saturated heterocyclic ring and the lone pair of electrons is available for reaction with protons (e.g. piperidine, Figure 3.19). Compounds of this type are similar in base strength to their open-chain aliphatic counterparts with typical pK3 values of 8-9. 

Based on elemental composition and relative molecular mass determinations, the formula of benzene was found to be C6H6. The saturated hydrocarbon hexane has the molecular formula C6H14 and therefore it was concluded that benzene was unsaturated. Kekule in 1865 proposed the cyclic structure 4 for benzene in which the carbon atoms were joined by alternate single and double bonds. Certain reactions of benzene, such as the catalytic hydrogenation to cyclohexane, which involves the addition of six hydrogen atoms, confirmed that benzene was a ring compound and that it contained three double bonds. However, since benzene did not undergo addition reactions with HC1 and HBr, it was concluded that these double bonds were different from those in ethene and other unsaturated aliphatic compounds. 

Reductions of a)S-unsaturated oxo-compounds with sodium borohydride may be complicated by saturation of the ethylenic bond, and by base-catalysed conjugate addition of alkoxide to give a 1,3-diol monoether. The factors controlling these reactions have been studied for a variety of aliphatic compounds, and the findings may prove useful in steroid chemistry. ... 

The bromine linked to a double bond or linked to an aromatic nucleus are much more stable structures (not easily decomposed to HBr as dibromo neopentylglycol, a saturated aliphatic bromine compound). Thus, a very successful bromine containing diol, produced industrially [4, 24], is based on tetrabromophthalic anhydride. Tetrabromophthalic anhydride is reacted first with diethylene glycol and the resulting half ester is reacted with propylene oxide (PO) (reaction 18.5) [3]. 

The oxidation of I2 in acetic anhydride in the presence of phosphoric acid was reported earlier to yield IPO4 however, the Mossbauer spectrum of the product clearly demonstrates that it should be treated as an iodine(i) compound.The yields of organic iodides produced in the reaction at 77 K of saturated aliphatic hydrocarbons with I and I2, generated by electron bombardment of I2 vapour, have been accounted for by a reaction mechanism involving cage effects. 

Structure of Benzene.—It is necessary at the outset to form a conception of the structure of the benzene molecule. Benzene contains but six hydrogen atoms in combination with six carbon atoms. This fact would lead to the view that the hydrocarbon is a highly unsaturated compound, as hexane, the paraffin which contains six carbon atoms, has the composition CeHu. In most of its reactions benzene acts like a saturated compound. Under certain conditions, however, it unites with bromine and forms the compound CeHeBre. If benzene were an unsaturated compound related to hexane, it should unite with eight atoms, as six carbon atoms joined as such atoms are joined in the aliphatic compounds, can hold in combination fourteen univalent atoms. This fact shows clearly that we must look for an arrangement of atoms in benzene quite different from that found among the unsaturated compounds of the aliphatic series. 

Allyl alcohol undergoes reactions typical of saturated, aliphatic alcohols. Allyl compounds derived from allyl alcohol and used industrially, are widely manufactured by these reactions. For example, reactions of aUji alcohol with acid anhydrides, esters, and acid chlorides yield aUyl esters, such as diaUji phthalates and allyl methacrylate reaction with chloroformate yields carbonates, such as diethylene glycol bis(allyl carbonate) addition of allyl alcohol to epoxy groups yields products used to produce allyl glycidyl ether (33,34). 

Non-volatile tritium-labelled compounds have been produced, but the degree of polymerization has been found to be not very high since the intermediate carbocations participate also in other reactions which lead to shortening of the chain length (equation 132). Reaction 132c seems to be the most probable. No simple saturated aliphatic hydrocarbon has been formed in the system C H3 — CH2=CH2 . In a mixture consisting of C H3, CH2—CH2 and H2O no n-alcohols containing more than two carbon atoms have been detected. This means that the isomerization of the carbocations formed is a faster process than their reactions with water or with ethylene. The reaction... 

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