Water adduct formation

The presence of water in the crystals can be explained by humid crystalization conditions and is proven by elemental analysis. The water adduct formation shows, that k 0, 0 -carboxylato ligands are hemilabile, chelating ligands, which can be easily displaced from one coordination site by a solvent. Thus, the carboxylato complexes 37a and 37b are equivalent to 16 VE fragments stabilized by the hemilabile carboxylato complexes. 

These ion-pair hydroxo rhodium(III) compounds are also strong bases (see Table I). It may be relevant to note here that Pt(PPh3)3 does not give any indication of water-adduct formation. 

Beuck, S., Schwabe, T, Grimme, S., et al (2009) Unusual mass spectro-metric dissociation pathway of protonated isoquinoline-3-carboxamides due to multiple reversible water adduct formation in the gas phase. Journal of the American Society for Mass Spectrometry, 20,2034-2048. 

The monomers are electron pair acceptors, and donor molecules are often able to split the dimeric halide molecules to form adducts thus, whilst the dimeric halides persist in solvents such as benzene, donor solvents such as pyridine and ether appear to contain monomers since adduct formation occurs. Aluminium halides, with the one exception of the fluoride, resemble the corresponding boron halides in that they are readily hydrolysed by water. 

Activated tertiary amines such as triethanolamine (TEA) and methyl diethanolamine (MDEA) have gained wide acceptance for CO2 removal. These materials require very low regeneration energy because of weak CO2 amine adduct formation, and do not form carbamates or other corrosive compounds (53). Hybrid CO2 removal systems, such as MDEA —sulfolane—water and DIPA—sulfolane—water, where DIPA is diisopropylamine, are aqueous alkaline solutions in a nonaqueous solvent, and are normally used in tandem with other systems for residual clean-up. Extensive data on the solubiUty of acid gases in amine solutions are available (55,56). 

The rather low values for the methylene groups of barbituric acid and its 2-thio derivative indicated a particularly easy adduct formation (84) which proceeds in water in excellent yield. 

In addition to systems of the above type, i.e. involving adduct formation, various other types of synergistic extraction systems are recognised and have been reviewed.4 An example is the synergistic influence of zinc in the extraction and A AS determination of trace cadmium in water.5... 

There is strong evidence that DNA adduction by these bulky reactive metabolites of PAHs is far from random, and that there are certain hot spots that are preferentially attacked. Differential steric hindrance and the differential operation of DNA repair mechanisms ensure that particular sites on DNA are subject to stable adduct formation (Purchase 1994). DNA repair mechanisms clearly remove many PAH/ guanine adducts very quickly, but studies with P postlabeling have shown that certain adducts can be very persistent—certainly over many weeks. Evidence for this has been produced in studies on fish and Xenopus (an amphibian Reichert et al. 1991 Waters et al. 1994). 

The Diels-Alder reaction of 4,6-dinitrobenzothiadiazole with cyclohexadiene shows only 40% adduct formation (across C-6 and C-7) after 7 days, and this was attributed to the poor electrophilicity as measured by the pA l2° values for water addition (pA, l2° 7.86) <2005TL8363>. The deep purple benzobis(thiadiazole) 109 undergoes a Diels-... 

A formally antiaromatic 1,4-dihydropyrazinothiadiazole has been prepared and characterized by single crystal X-ray spectroscopy. The antiaromatic character of which has been supported computationally using NICS measurements <20070L1073>. CHIH-DFT computational studies on acenaphtho[l,2-f]-l,2,5-thiadiazole 1,1-dioxide led to simulations of its infrared (IR) and ultraviolate (LJV) spectra, the dipole moment and polarizability <2007JMT373>. 4,6-Dinitrobenzothiadiazole was determined to have an electrophilic reactivity of —8.40 which corresponds to a pK z° of 7.86 for Meisenheimer complexation with water and is close to the demarcation boundary (E = —8.5) between super-and normal-electrophiles and between reactive dienophiles and inert partners in Diels-Alder adduct formation <20070BC1744>. 

The first step in the hydrolysis reaction is the formation of the water adduct [Eq. (23)] [69], which subsequently eliminates alkane to yield the hydroxide R2A10H. At elevated temperatures, further alkane elimination is observed with the formation of alkyl-alumoxane [67, 68]. Structurally characterized alumoxanes are listed in... 

The generation of HO by pulse radiolysis provides a way for investigating the kinetics of hydroxyl spin adduct formation. For PBN and some of its 4-substituted derivatives (ranging from 4-MeO to 4-N02), rate constants in the range of (5-9) X 109 dm3 mol 1 s 1 were determined (Greenstock and Wiebe, 1982). A study of the reaction of the water-soluble 2-, 3- and 4-PyBN[23] and HO showed that most of the hydroxyl radicals became attached to the heteroaromatic ring (Neta et al., 1980 Sridhar et al., 1986). Similar findings... 

This chapter provides the groundwork of solution chemistry that is relevant to solvent extraction. Some of the concepts are rather elementary, but are necessary for the comprehension of the rather complicated relationships encountered when the solubilities of organic solutes or electrolytes in water or in nonaqueous solvents are considered. They are also relevant in the context of complex and adduct formation in aqueous solutions, dealt with in Chapter 3 and of the distribution of solutes of diverse kinds between aqueous and immiscible organic phases dealt with in Chapter 4. 

APCI also relies on protonation, deprotonation or adduct formation, but these occur in the gas phase. Water and/or alcohols form the protic solvents that mediate the ionisation process. Thermal energy is imparted into the eluent to desolvate the solute molecules, and fewer collisions occur in the gas phase to dissipate internal energy than in solution. For this reason it tends to be less suitable than... 

The question arises as to the actual sequence of events that end up in the reduction of dioxygen into water. Even though complementary investigation is needed before a complete answer could be proposed, several observations are worth mentioning provisionally. The reoxidation of reduced heteropolyanions by dioxygen after the catalytic processes in which they participate is a popular practice. Its mechanism was generally and indistinctly explained to go through an intermediate adduct formation accompanied by inner sphere electron transfers [164]. 

Despite these widespread applicahons, ILM is not equally well suited for all classes of analytes. Due to the need for increased laser energies/fluences for the ionizahon/desorption process, ILMs may only be of restricted suitability for some classes of analytes. For example for proteins, an extensive peak broadening caused potenhally by the combination of extended neutral losses (e.g., of ammonia or water) and alkali-ion-adduct formation can be observed. On the other hand, the increased tendency of the ILM to favor sodium and potassium adduct formation makes it ideally suited for the measurement of carbohydrates [38,40], whereas in proteomics, this tendency of adduct formahon is again an unwanted effect. 

Human liver preparations metabolize ethylene dibromide to water-soluble and irreversibly protein- and DNA-bound metabolites by both cytochrome P450 and glutathione S-transferase (GST) enzymes (Wiersma et al., 1986). DNA adduct formation occurs also in isolated human hepatocytes (Cmarik et al., 1990). 

Adduct formation with OH" occurs under very mild conditions (bicarbonate solution), and a solution of 160 in water displays the UV-visible spectrum of the adduct, indicating extensive conversion of the starting compound.202... 

Alcoholates of nonreducing saccharides (soluble or insoluble) and of saccharide derivatives may also be prepared by the method of Wolfram and coworkers.92-9 A mixture of the carbohydrate and sodium hydroxide in 1-butanol is refluxed, preferably under a nitrogen atmosphere, find all of the water of formation is removed by concurrent azeotropic distillation. This method is preferred when no trace of hydroxide adduct or water is desired in the Anal product. Butoxide ion is a possible contaminant, how-... 

The SO 3 is readily converted to sulfuric acid in the presence of water vapor [6,7], An experiment employing 1803 provided evidence for acyclic adduct formation as originally proposed by Martinez et al. [127]. The ratio /c55//c54 was calculated to be (4.9 2.0) x 10 15 cm3 molecule. At any rate, the reaction of CH200 with S02 does not appear to be a simple bimolecular O-atom transfer reaction. 

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