Amines Compared with Alcohols

The Feltzin mechanism 73) takes account of the presence of proton donors at the beginning of copolymerization. However, initiation probably proceeds in two ways 74) and depends on the type of the proton donor and its concentration in the copolymerization mixture. If HA in Eq. (45) is alcohol, phenol or moisture, initiation occurs according to Eq. (46), i.e. through interaction with the anhydride yielding an ammonium salt of the monoester. The formation of monoesters as primary active centres accounts here for the lower cocatalytic effect of phenols as compared with alcohols. If the proton donor is a carboxylic acid, activation of the tertiary amine (Eq. (63)) is followed by reaction with the epoxide according to Eq. (76)74. ... 

Compared with alcohols, which possess a high standard potential of oxidation, moderate nucleophilicity and weak basicity, amines very often serve as good electron donors and relatively strong bases and nucleophiles in chemical reactions. Photoinduced electron transfer (PET) processes, in which an amine donates an electron to the reaction partner in either its ground or excited electronic state, result in the formation of an amine substrate exciplex (Scheme 6.196).670 1224 The driving force for electron transfer is related to the standard potential of oxidation of the donor, the standard potential of reduction of the acceptor and the excited state energy of the absorbing partner (see Chapter 4). 

Dipole-dipole interactions, especially hydrogen bonding, are present in amines but absent in alkanes. The less polar nature of amines as compared with alcohols, however, makes these intermolecular forces weaker in amines than in alcohols. 

Considerable rate enhancements have been observed when water is used as solvent compared with alcoholic or hydrocarbon media for Mannich reactions, i.e. condensations of ketones with secondary amines in the presence of formaldehyde [65]. Allylsilanes [66] and allylstannanes [67] in aqueous media were used in organic synthesis under Mannich-like conditions. More recently, Kobayashi reported the catalysis of the reaction of vinyl ethers with iminium salts by ytterbium triflate in tetrahydrofuran-water mixtures [68]. 

Most aromatic acid chlorides impart a strongly acid reaction when shaken with water (compare Section 111,88). All are completely hydrolysed by boiling with solutions of caustic alkalis and yield no product volatile from the alkaline solution (compare Eaters, Sections 111,106 and IV, 183). They may be distinguished from acids by their facile reactions with alcohols (compare Section 111,27), phenols (compare Section IV,114), and amines (compare Sections 111,123 and IV.lOO). 

The shift towards the monoaminocarbonylation, obtained under these conditions, as compared with the dialkoxycarbonylation observed in alcoholic solvents, is due to the basicity of the amine, which favors the formation of an alkynylpalladium complex (Scheme 37). This species then inserts carbon monoxide with formation of an alkynoylpalladium intermediate, which undergoes nucleophilic displacement by R2NH to give the final 2-ynamide. 

The need for great care to avoid the possibility of detonation of perchloryl compounds by exposure to shock, overheating or sparks is stressed. The compounds are generally more sensitive to impact than mercury fulminate and are of comparable sensitivity to lead azide [1], A range of highly explosive alkyl perchlorates [2] and perchlorylamines [3] have been prepared by interaction of dichlorine heptaoxide with alcohols or amines in carbon tetrachloride solution. The solutions of the products were not sensitive to mechanical shock and could... 

It is worth mentioning that the extent of asymmetric induction in the sulfinate synthesis is comparable with that observed in the reaction of sulfinyl chlorides with optically active alcohols. However, in this case, the sulfinate products contain only one chiral center on sulfur the chiral-inducing amine is very easily recovered as the hydrochloride. 

A number of nucleophiles including CN , BH4, amines and alcohols react with coordinated nitriles at lO" enhanced rates compared with the free ligand. One of the most novel examples involves as a nucleophile. Acetonitrile and sodium azide form 5-methyltetrazole only after 25 hours at 150°C whereas the cobalt(III) coordinated acetonitrile reacts in 2 hours at room temperature ... 

Although the initial report included amine nucleophiles, the scope was limited to activated amines such as indole (which actually undergoes C-alkylation at the 3-position), phthalimide, and 7/-methylaniline. Furthermore, enantioselectivities were inferior to those observed with alcohols as nucleophiles. Lautens and Fagnou subsequently discovered a profound halide effect in these reactions. The exchange of the chloride for an iodide on the rhodium catalyst resulted in an increased enantioselectivity that is now comparable to levels achieved with alcoholic nucleophiles ... 

In a recent example metalloporphyrins are used as the sensing dyes for a wide variety of odorants, including alcohols, amines, arenes, ethers, halocarbons, ketones, phosphines, thioethers and thiols. An array of four different metalloporphyrins are placed on a substrate and exposed to the vapours for 30 s. The various vapour molecules coordinate onto the central metal atoms of the porphyrins, causing them to change colour and producing a unique four-colour array. The resulting colour array is compared with a library of known chemicals or mixtures and identification is achieved. 

When R and/or R1 = H, an M - 1 peak is usually visible. This is the same type of cleavage noted above for alcohols. The effect is more pronounced in amines because of the better resonance stabilization of the ion fragment by the less electronegative N atom compared with the O atom. 

Comparing Tables I and II reveals that amine concentration is the second important variable in the aldehyde hydrogenation reaction. For a given amine, selectivity to alcohol passes through a maximum with increasing concentration of N donor. Thus with DMBA, the alcohol present at 80% olefin cvonversion was 5, 29, and 28% at 1, 2, and —3M (resin), respectively, suggesting an optimum DMBA concentration of about 2M. 

As shown in Figure 3, a positive p-value (+0.92) was observed in the hydrogenation of substituted benzaldehydes, giving strong support to the postulation by Heil and Marko that the rate determining step in the formation of alcohol (Mechanism 2) is the hydride addition step. It is therefore suggested that coordination of amine to rhodium increases the hydridic character of the Rh-H bond, much the same as is postulated in cobalt-tributylphosphine complexation (20). The differing effect of amine on rhodium (promoter) and on cobalt (inhibitor) is attributed to the more hydridic nature of a Rh-H bond as compared with the very protonic HCo(CO)4. Addition of amines to HCo(CO)4 results in formation of inactive species similar to I. 

Allylic alcohols also may be arylated in / /-methylpyrrolidinone or DMF solution with sodium bicarbonate as the base.81 The use of this base improves the yields of aldehydes obtained compared with tertiary amine bases in the case of aryl bromides with electron-withdrawing substituents, where reduction to an arene is sometimes a problem,... 

The intermolecular attractive force due to hydrogen bonding is greater between alcohols than it is between amines because of the greater polarity of an O-H bond compared with an N-H bond. 

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