Low molecular weight amines

Reactivity Acrolein is a highly reactive chemical, and contamination of all types must be avoided. Violent polymerization may occur by contamination with either alkaline materials or strong mineral acids. Contamination by low molecular weight amines and pyridines such as a-picoline is especially hazardous because there is an induction period that may conceal the onset of an incident and allow a contaminant to accumulate unnoticed. After the onset of polymeriza tion the temperature can rise precipitously within rninutes. 

Detergent Additives. Diesel engine deposits ate most troublesome in the fuel dehvery system, ie, the fuel pump and both fuel side and combustion side of the injectors. Small clearances and high pressures mean that even small amounts of deposits have the potential to cause maldistribution and poor atomization in the combustion chamber. The same types of additives used in gasoline ate used in diesel fuel. Low molecular weight amines can also provide some corrosion inhibition as well as some color stabilization. Whereas detergents have been shown to be effective in certain tests, the benefit in widespread use is not fully agreed upon (77). 

One other characteristic of amines is their odor. Low-molecular-weight amines such as trimethyjamine have a distinctive fishlike aroma, while diamines such as 1,5-pentanediamine, commonly called cadaverine, have the appalling odors you might expect from their common names. 

Triple bonds can also be selectively reduced to double bonds with DIBAL-H, " with activated zinc (see 12-36), with hydrogen and Bi2B-borohydride exchange resin, ° or (internal triple bonds only) with alkali metals (Na, Li) in liquid ammonia or a low-molecular-weight amine.Terminal alkynes are not reduced by the Na—NH3 procedure because they are converted to acetylide ions under these conditions. However, terminal triple bonds can be reduced to double bonds by the... 

Reduction of acetylenes can be done with sodium in ammonia,220 lithium in low molecular weight amines,221 or sodium in HMPA containing /-butanol as a proton source,222 all of which lead to the A-alkene. The reaction is assumed to involve successive electron transfer and protonation steps. 

The concept of repetitive growth with branching was first reported in 1978 by Vogtle [4] (University of Bonn, Germany) who applied it to the construction of low molecular weight amines. This was followed closely by the parallel and independent development of the divergent, macromolecular synthesis of true dendrimers in the Tomalia Group [5,6] (Dow Chemical Company). The first... 

Nanomolar concentrations of low molecular weight amines and organic acids dissolved in seawater can be preconcentrated up to 1000-fold by diffusion across hydrophobic membranes and collecting in HC1 or NaOH solutions, respectively. Of a set of 25 amines investigated, excepting pyrrole, all showed practically quantitative trapping efficiency76. 

Histamine (2-[4-imidazole] ethylamine) is a low-molecular-weight amine synthesized from L-histidine exclusively by histidine decarboxylase. It is produced by various cells throughout the body, including central nervous system neurons, gastric mucosa parietal cells, mast cells, basophils and lymphocytes [1-4]. Since its discovery as a uterine... 

The compatibility of the quaternary amlne-contalnlng NTMP with the nltrlle-modlfled epoxy adhesive, which leads to a bond that falls only within the adhesive (l.e., cohesive failure) can be explained. The FM 123-2 adhesive contains the storage-stable curing agent, dlcyanodlamlde, which does not release low-molecular weight amines until It becomes soluble In the resin above 90°C. (Equation 2) (25)... 

Sodium and lithium are the most common metals, and diethyl ether, tetrahydro-furan, and HMPA are often used as cosolvents to overcome solubility problems. The Benkeser method,37 204 employing lithium in low-molecular-weight amines (methylamine, ethylamine, ethylenediamine), is a more powerful reducing agent... 

The following is valid, only when GA is reacted with low molecular weight amines. 

It has already been reported that the weight loss of as-synthesized MMSs depends on the kind of the template used in the synthesis [17]. This is an obvious consequence of the fact that different templates decompose and thermodesorb at different temperatures. However, it was somewhat unexpected that the decomposition/desorption of the same kind of the template may be dramatically influenced by the framework composition of materials [4,10-14]. This can be understood as an influence of the framework structure on the process of Hoffmann elimination of alkylammonium to the corresponding alkene and low molecular weight amine [4,8], This decomposition process leads not only to the elimination of the electrostatic framework-template interactions but also to the formation of decomposition products of lower molecular weight than that of the surfactant. Thus, the framework-surfactant interactions are crucial factors determining the thermogravimetric behavior. 

The known or suspected neurotransmitters in the brain already number several dozen (Table 1-1). Based on theoretical considerations of the amount of genetic material in neurons, there may be several hundred to several thousand unique brain chemicals. Originally, about half a dozen classical neurotransmitters were known. In recent years, an ever increasing number of neurotransmitters are being discovered. The classical neurotransmitters are relatively low molecular weight amines or amino acids. Now we know that strings of amino acids called peptides can also have neurotransmitter actions, and many of the newly discovered neurotransmitters are peptides, which are specifically called neuropeptides (Fig. 1-9). 

Polyurethanes (PU) The odor of many polyurethanes is caused by fishy smelling low molecular weight amines, mostly methylamines like trimethylamine, degradation products of the amine catalysts used during production. In some cases after evaporation of the fishy smelling amines, other odor qualities remain. One noticeable odor of PU samples was earthy, nutty, which can often be attributed to substituted pyrazines, formed by condensation of two a-aminoketones, subsequent oxidation or alkylation by aldehydes. One example is 2-ethyl-3,5-dimethylpyrazine (Mayer and Breuer, 2006). 

However, all amines can participate in hydrogen bonding with protic solvents, so amines have similar water solubilities to comparable alcohols. Low molecular weight amines are freely miscible with water. Low molecular weight amines have an offensive fishlike smell. 

There are a number of similarities between ammonia and amines that carry beyond the structure. Consider odor. The smell of amines resembles that of ammonia but is not as sharp. However, amines can be quite pungent. Anyone handling or working with raw fish knows how strong the amine odor can be, since raw fish contains low-molecular-weight amines such as dimethylamine and trimethylamine. Other amines associated with decaying flesh have names suggestive of their odors putrescine and cadaverine. 

The solubility of low-molecular-weight amines in water is high. In general, if the total number of carbons attached to nitrogen is four or less, the amine is water soluble amines with a carbon content greater than four are water insoluble. However, all amines are soluble in organic solvents such as diethyl ether or dichloromethane. 

Two major classes of amphoteric surfactants are derived from fatty alkyl hydroxyethyl imidazolines which, in turn, are produced from fatty acids and low molecular weight amines. Because fatty acids are fairly economic, the imidazoline derived amphoacetates tend to be less expensive than the iminodipropionates discussed above. Most imidazoline derived... 

In the case of PVA, while AG° varies continuously with a, AH0 remains constant in a large range of pH s (a = 0.5-0). This means that only the entropy term AS0 is responsible for the pK variation in the above range. A comparison with a simple tetraamine (triethylenetetramine) shows that all the thermodynamic values for PVA are similar to those obtained with simple low molecular weight amines. 

Molecular sieves such as zeolite have also been used as carriers for low-molecular-weight amines. An amine, such as DETA, can be absorbed into the sieve prior to mixing with an epoxy resin. The sieve protects the amine from reacting with the epoxy resin, and a relatively long shelf life is possible. Release of the DETA is then initiated by heat or through displacement by atmospheric moisture. 

Gejvall [114] analysed low-molecular-weight amines in the form of urethanes produced by their reaction with diethyl dicarbonate (Scheme 5.12). The reaction can be carried out in aqueous solution. A 10-mg amount of diethyl dicarbonate was allowed to react with 0.05—0.7 mg of the amine at room temperature for 30—40 min, the pH being adjusted to 9.5 with NaOH. A good separation with symmetric peaks was obtained by using SE-30 as the stationary phase. 

Chloramines are considered as main products secondary to hypochlorite formation. Taurine is one of the most abundant sources of free amino groups in polymorphonuclear neutrophilic leukocytes, representing approximately 50% of all low-molecular-weight amines released by PMNs (G24, Z5), and taurine chloramine is formed immediately along with MPO-mediated HOC1 synthesis ... 

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