Organic acids deprotonation

AEC is the preferred technique since rain samples can be injected directly after maybe filtration as pretreatment [2-7]. Injection volumes are typically quite low, i.e., 10—50 pL. At the high pH of the eluent (usually NaOH), organic acids deprotonate to their anionic form, which makes them amicable for separation on anion-exchange columns. A guard column often precedes the analytical column so that the analytical column is protected... 

Compounds with an acidity constant, pK, in the range of 4 to 10, i.e. weak organic acids or bases, are present in two species forms at ambient pH. This pA a.i. range includes aromatic alcohols and thiols, carboxylic acids, aromatic amines and heterocyclic amines [15]. Conversely, alkyl-H and saturated alcohols do not undergo protonation/deprotonation in water (pA iw 14). 

It is common practice in pharmaceutical industry to generate salt forms of a drug substance to improve solid-state properties and solubility. CE has proven its ability to analyze reliably organic acids (direct, indirect detection) and alkaline/earth alkaline metals and basic amino acids. For basic drugs, a non-toxic organic acid or inorganic acid is chosen as counterion. Acidic drug substances will usually be deprotonated by alkaline and earth alkaline... 

Alonso et al. (2005) described anion-radical proton abstraction from prochiral organic acids. If the anion radicals were formed from homochiral predecessors, asymmetric deprotonation can be reached. However, low reactivity of the anion radical is required Slow proton transfer, that is, high activation energy of the reaction discriminates well between diastereoselective transition states. 

BuNa/TMEDA/hexane is comparable to BuLi/TMEDA. Thus it deprotonates weak organic acids. Benzylsodium-TMEDA (made from toluene) is obtained as yellow needles. BuK/TMEDA, prepared in the same way, metallates hydrocarbons more readily than BuNa/TMEDA, but also decomposes more readily.1... 

In many SN2 reactions, the nucleophile is generated by deprotonation of an organic acid. For each molecule, choose the base best suited to completely remove the labeled proton. (Consider pK values and recognize that, in some cases, dianions should be considered.) Explain your answers. 

R-Li (alkyllithium) Methyllithium Butyllithium sec-Butyllithium fert-Butyllithium Strong base Strong nucleophile when R is not bulky. Deprotonation of weak organic acids, E2 eliminations Sn2/Sn2 displacements, addition reactions, addition-elimination reactions... 

R2N-Li (lithium dialkylamide) Lithium diisopropylamide Strong base, not nucleophilic when R is bulky. Deprotonation of weak organic acids with acidities as high as pKa 35... 

M-OH (metal hydroxide) Sodium hydroxide Potassium hydroxide Nucleophilic bases Deprotonation of organic acids with acidities as high as pKa = 16, hydrolysis of esters, amides, and nitriles... 

R3N (trialkylamine) Triethylamine Diisopropylethylamine Not nucleophilic base Deprotonation of organic acids, acid scavenger... 

A similar acid-base reaction does not occur when cyclohexanol is treated with NaOH because organic alcohols are much weaker organic acids, so they can only be deprotonated by a very strong base such as NaH. NaOH is not strong enough to form significant amounts of the sodium alkoxide. 

Acid-base indicators are weak organic acids (denoted by the symbol IH) whose deprotonation is accompanied by a color change ... 

In contrast to this mechanistic concept, Schwab et al. [9] surprisingly found, that P-alanine itself is not a substrate for the CALB-catalyzed polyamide formation. This can be understood in the light of a recent publication by Hollmann et al. [16] who could demonstrate that organic acids having a pKa value of <4.8 irreversibly inhibit CALB, presumably by protonation of His224, which in turn prevents the deprotonation of Ser s necessary as part of the catalytic process. P-Alanine has a first pKa of 3.6 [17] which clearly is below the critical value. Therefore, if P-alanine is generated in larger amounts is will reduce the overall enzyme activity by deactivation. Furthermore, Schwab et al. [4] only achieved low... 

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