Amine hydrogen-bonding

Usually, the influence of the solvent on the proton donor and acceptor interactions is relevant95. The importance of the amine/solvent hydrogen bonding interaction depends on the strength of the amine/amine hydrogen bonding interaction96. 

Aviv and Gross developed an interesting insertion reaction of diazo compounds into a secondary amine-hydrogen bond in the presence of Fe-corrole complexes (Scheme 7.8) [12], Competition experiments performed in the presence of an amine and an alkene revealed the N—H-insertion reaction to be much faster than the cyclopropanation of the C=C bond. Apart from this chemoselectivity issue, the reactions are characterized by their very short reaction times most insertion reactions were completed within 1 min at room temperature. Most recently, Woo s group reported on a similar process using commercially available iron tetraphenyl-porphyrin [Fe(TPP)] dichloride [13]. 

Don t become confused by memorizing too much detail about the physical properties of ammonia and amines. For the MCAT, just Keep in mind that ammonia and amines hydrogen bond, which raises boiling point and increases solubility. 

Fluorescence in INpOH-aliphatic amine hydrogen-bonded systems in nonpolar rigid matrices like polyethylene films at 77 K is dual in nature [200-202], The ESPT in the hydrogen-bonded complex results in two types of ion pairs, one with in-plane orientation between excited naphtholate and ammonium ions (fluorescence maximum at 395 nm with a lifetime of 5.3 nsec) and the other with an... 

It has recently been shown that within the same reaction series the mechanism of catalysis by uncharged Lewis bases may change with variation of the structure (275). Tandem kinetic and IR hydrogen bond studies revealed that silylation reaction of a silanol catalyzed with triethylamine is first order with respect to the silanol-amine hydrogen bond complex [Eq. (75).] The same reaction was shown to be effectively catalyzed by... 

Yamdagni, R., and Kebarle, R, Gas-phase basicities of amines. Hydrogen bonding in proton-bound amine dimers and proton-induced cyclization of a,a-diamines, J. Am. Chem. Soc. 95, 3504-3510(1973). 

One method we have developed for avoiding polymerization with the adsorbed water layer is to use a base catalyzed reaction in supercritical CO2 (SCF CO2). We have shown that SCF CO2 has the unique property of removing all adsorbed water from the silica surface. Once removed the amine base catalyses the reaction of the silane with the surface. As shown in Figure 1, the preadsorbed amine hydrogen bonds to the surface silanol and renders the Si-0 group of the silanol more nucleophilic for reaction with the silicon atom of the incoming chloro or alkoxysilane. Triethylamine is the preferred amine as it binds to all isolated silanols from SCF CO2 and is not removed with subsequent exposure to flowing SCF CO2 solvent. Furthermore a tertiary amine should be used as primary and secondary amines such as ammonia are known to react with CO2 to produce carbamates. " ... 

One year later, Rahaman et al. reported a cascade reaction of aldehyde and nitro alkanes for the synthesis of functionalized y-nitro aldehydes with high reactivity [33], Generation of the intermediate nitro alkenes involved cooperative secondary amine/hydrogen bonding-promoted condensation of nitromethane and aldehydes. Consequently, the newly formed nitro alkenes promptly participated in the next cycle cocatalyzed by the two catalysts (Scheme 9.37). 

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