Acids trends

Nicholls, D. and Attwell, D. The release and uptake of excitatory amino acids. Trends Pharmacol. Sci. 11 4624 68,1990. 

Structural analysis of hydroxylamines, oximes and hydroxamic acids Trends and patterns... 

In addition to ice formation, salts also precipitate as these solutions are lofted to higher altitudes. A consequence of the formation of these solid phases (ice and salts) and the low-temperature eutectics of strong acids (Fig. 3.5) is that the atmospheric solutions become more and more acidic with altitude (Fig. 5.8). For example, the final elevation (temperature) examined is 11.54 km (—50 °C). At this point, the calculated concentrations of the Hubbard Brook solution are H+ = 7.55m with acid anions (Cl-, NO3, SO4-, HSOJ) = 7.91m. Similarly, for the Mt. Sonnblick solution, H+ = 6.50 m and acid anions = 6.90 m. These acidic trends are in line with stratospheric chemistries, which are predominantly sulfuric/nitric acid aerosols (Carslaw et al. 1997). For example, the total acid concentration at 20.7km in the stratosphere is 10.17m (calculated from fig. 7 in Carslaw et al. 1997), which is in line with our lower atmospheric concentrations. 

Certik, M., Sakuradani, E., and Shimizu, S. 1998. Desaturase-defective fungal mutants useful tools for the regulation and overproduction of polyunsaturated fatty acids. Trends Biotechnol., 16, 500-505,1998. 

Wong, C.G.T., K. M. Gibson, and O. C. Snead. From the Street to the Brain Neurobiology of the Recreational Drug Gamma-hydroxybutyric Acid. Trends in Pharmacological Sciences 25 (1) (2004) 29-34. 

Neglecting solvent effects is extremely hazardous. Equilibria and kinetics can be dramatically altered by the nature of the solvent For example, the rate of nucleophilic substitution reactions spans 20 orders of magnitude in going from the gas phase to polar and nonpolar solvents. A classical example of a dramatic solvent effect on equilibrium is the tautomerism between 1 and 2. In the gas phase, the equilibrium lies far to the left, while in the solution phase, 2 dominates because of its much larger dipole moment." Another classical example is that the trend in gas-phase acidity of aliphatic alcohols is reverse of the well-known trend in the solution phase in other words, in the solution phase, the relative acidity trend is R3COH < R2CHOH < RCH2OH, but the opposite is true in the gas phase. ... 

Shelp, J., Bown, A.W. and McLean, M.D. (1999) Metabolism and function of gamma-aminobutyric acid. Trends in Plant Scl, 4,446-52. 

Examine acidity trends across a row of the periodic table by comparing CH4 and H2O, two compounds having H atoms bonded to a second-row element. We know from Table 2.1 that H2O has a much lower pAg and therefore is much more acidic than CH4, but why is this the case ... 

Now examine acidity trends down a column of the periodic table by comparing H-E and H-Br. Once again, first draw both conjugate bases and then determine which is more stable. In this case, removal of a proton forms E and Br . 

Samuel J, Bertozzi CR. Chemical tools for the study of polysialic acid. Trends Glycosci. Glycotech. 2004 16(91) 305-318. 

Nordli DR. DeVivo DC. The ketogenic diet revisited back to the future. Epilepsia 1997 38 743-749. Ordway RW, 8inger JJ, Walsh JVJ. Direct regulation of ion channels by fatty acids. Trends Neurosci 1991 ... 

The acidity trend is consistent with the above analysis. Taking into account that these solvent systems differ only in the nature of the anion and that a values are mainly determined by the nature of the cation, the behaviour can be connected with an anion effect on the acidity. The positive deviation manifested in some solvents with [bmim][BF ] and [bmim][PF ] and the slight synergetic effect can be attributed to the strong intersolvent interactions mentioned above. The almost Unear decrease of the property in several mixtures comprised of [bmim][Cl] and [bmim][Br] also demonstrates that the mixed solvent is less favoured, although a slight negative deviation in some solvents with [bmim][Cl] can be noticed. 

R. Schauer. Origin and biological role of the great chemical diversity of natural sialic Acids. Trends in Glycoscience and Glycotechnology 1997, 9, 315-330. 

Boncinelli, E., Simeone, A., Acampora, D., Mavilio, F. 1991. HOX gene activation by retinoic acid. Trends Genet. 7, 329-334. 

FIGURE 4.1 The pathway for the formation of GABA in tea. (From Shelp, B. J., McLean, M. D., and Bown, A. W. 1999. Metabolism and functions of y-aminobutyric acid. Trends Plant Sci. 4 446-52. With permission.)... 

A series of hydrocarbons has been studied in cyclohexylamine, using cesium cyclohexylamide as base. For many of the compounds studied, spectroscopic measurements were used to determine the relative extent of deprotonation of two hydrocarbons and thus establish relative acidity. For other hydrocarbons, the acidity was derived by kinetic measurements. It was shown that the rate of tritium exchange for a series of related hydrocarbons is linearly related to the equilibrium acidities of these hydrocarbons in the solvent system. This method was used to extend the scale to hydrocarbons such as toluene for which the exchange rate, but not equilibrium data, can be obtained. Representative values of some hydrocarbons with pK values ranging from 16 to above 40 are given in Table 6.2. The pK values of a wide variety of organic compounds have been determined in DMSO, and some of these values are listed in Table 6.2 as well. It is not expected that these values will be numerically identical with those in other solvents, but for most compounds the same relative order of acidity is observed. For synthetic purposes, carbanions are usually generated in ether solvents, often THF or DMF. There are relatively few quantitative data available on hydrocarbon acidity in such solvents. Table 6.2 contains a few entries for Cs salts. The numerical values are scaled with reference to the pK of 9-phenylfluorene. ° The acidity trends are similar to those in cyclohexylamine and DMSO. 

Ma JF, Ryan PR and Delhaize E (2001b) Aluminium tolerance in plants and the complexing role of organic acids. Trends Plant Sd 6 273-278. 

Davis and coworkers [104] studied " Xe NMR of xenon adsorbed in several SAPOs, ALPOs, and Y zeolites. From a comparison of the xenon chemical shift extrapolated to zero pressure, these authors concluded that Xe atoms feel significantly smaller electrostatic fields and field gradients in the aluminophosphates compared to aluminosilicates. The extrapolated chemical shift decreased from 97 ppm in erionite to 60 ppm in Y zeolite and to 27 ppm in AIPO4-5, with the values for SAPOs being intermediate to Y zeolites and AlPOs as would be expected from the acidity trends. They concluded as well that SAPO-37 does not contain separate aluminophosphate and aluminosilicate islands. Dumont et al. [105] also carried out xenon NMR experiments in SAPO-37. From xenon sorption capacity and the decrease in the chemical shift, their conclusion was that the framework of calcined SAPO-37 is unstable when exposed to moist air. 

The same general acidity trends are observed in aqueous solution. The three heaviest hydrohalic acids—HCl, HBr, and HI— are equally strong in water because of the leveling effect. All the other binary hydrogen compounds are weaker adds, their strength decreasing toward the left in the periodic table. Methane and ammonia exhibit no acidic behavior in aqneous solution, nor do silane (SiH4) and phosphine (PH3). 

Drusch S, Mannino S (2009) Patent-based review on industrial approaches for the microencapsulation of oils rich in polyunsaturated fatty acids. Trends in Food Science and Technology 20 237-244. 

Nelson, P.T., Stefansson, K., Gulcher, J. and Saper, C.B. 1996. Molecular evolution of tau protein Implications for Alzheimer s disease. J. Neurochem. 67 1622-1632 Nicholls, D. and AttweU, D. 1990. The release and uptake of excitatory amino acids. Trends Pharmacol. Sci. 11 462-468... 

Internal market analysis of bio-PA market based on sebadc acid trends. 

For an opposing view, see Devarajan, D., Gustafson, S. J., Bickelhaupt, F. M., Ess, D. H. (2015). Is There a Need to Discuss Atomic Orbital Overlap When Teaching Hydrogen-Halide Bond Strength and Acidity Trends in Organic Chemistry Journal of Chemical Education, 92(2), 286-290. 

De Keukeleire, D., J. Vindevogel, R. Szucs, and P. Sandra, The history and analytical chemistry of beer bitter acids, Trends Anal. Chem., 11, 275-280 (1992). 

Gal et looked at the acidity trends in ajS-unsaturated alkanes, silanes. 

Kohn, J. (1993) Design, syntliesis, and possible applications of pseudo-poly(amino acids). Trends Polym. S ., 1(7),206-21X... 

Using F2PN(CH3)2 as a ligand and metal halides as acids trends in chemistry can be established. 

This electronegativity difference due to the hybridization states of carbon should manifest itself in other acidity trends. Indeed, it does. Examine the trends in acidities of alcohols and carboxylic acids given in Tables 5.5F and G, respectively. Proximity of the acidic group to an alkynyl group results in the strongest acid, whereas a simple alkyl group gives the weakest acid. 

Floyd T R, Crowther J B, Hartwick R A 1985 HPLC of nucleic acids trends in the separation of synthetic single-stranded oligonucleotides and double-stranded DNA fragments. LC Mag 3 508-512, 516-520... 

Blanco C.A., Rojas A., CabaUera P.A., Ronda F., Gomez M., CabaUera L A better control of beer properties by predicting acidity of hop iso-a-acids. Trends in Food ScienceandTechnology, 17 yTi-yn (2006). 

Novakova, L., P. Solich, and D. Solichova. 2008. HPLC methods for simultaneous determination of ascorbic and dehydroascorbic acids. Trends Anal. Chem. 27 942-958. 

---