Amine group titration

C18-0142. The amine group of an amino acid readily accepts a proton, and the protonated form of an amino acid can be viewed as a diprotic acid. The p Zg values for serine (H2 NCHRCO2 H, i = CH2 OH) are p ra(H3 N"") =9.1 and p (002 H) - 2.2. (a) What is the chemical formula of the species that forms when serine dissolves in pure water (b) If this species is titrated with strong acid, what reaction occurs (c) 10.00 mL of 1.00 M HCl is added to 200. mL of 0.0500 M serine solution. This mixture is then titrated with 0.500 M NaOH. Draw the titration curve, indicating the pH at various stages of this titration. 

All dendrimers consist of inner tertiary amines, located at the branching points of the various dendritic shells (layers). The amine-terminated dendrimers, furthermore, have basic primary amine end-groups. Basicity is therefore one of the most dramatic properties of the polypropylene imine) dendrimers, and has been studied via titration experiments and calculations. Titration experiments of the dendrimers have been performed in water using 1 M hydrochloric acid. Only two equivalence points are observed for DAB-J nJr-(NH2)4 in a ratio of 2 1. From these titrations, pKa values of 10.0 (primary amine groups) and 6.7 (tertiary... 

The most reliable and convenient method to determine the total (end group and isocyanate) NCO is titration. A known amount of an amine (dibutylamine is used in the reference) is added to a weighed amount of prepolymer in solution. The amine reacts with the NCO groups and the excess amine, if titrated with a standard HCl solution, to a bromothymol blue end point. The amount of NCO is calculated as milUequivalents per gram of prepolymer or mass percent of NCO. Both measures are appropriate. 

Although the pK of the cy-amine group for Lys is within the titratable range and that for Arg would probably become so on coordination, the relatively long methylene chains render any tridentate chelation unlikely, and this appears to be the case.10- 4 The shorter methylene side chains in the synthetic diamine-monocarboxylates ornithine, 2,4-diaminobutanoic acid and 2,3-diamino-propionic acid lead to increased tridentate behaviour in that order. 

We found no enhanced basicity attributable to the amine group on amino-propylsilane-treated glass, as reported by every other investigator cited above except Fowkes et al. [7], Using calorimetric phenol titration, they found that an equivalent basicity was imparted to glass fiber by aminopropylsilane and two other silanes all three were more basic than bare glass. 

Polyamide microcrystalline powders form measurable polymer-bound fluorescent reaction products with malonaldehyde from oxidizing lipids and with reducing sugars. The compounds form on the terminal amine groups which appear to exist in zwitterionic fields with carboxylate anions, as revealed by titration with acid, alkali, or benzoquinones. 

In acetonitrile/dichloromethane solution this type of dendrimer shows three kinds of emission bands having their origin in the excited state localised within the naphthyl group, a naphthyl excimer, and a naphthyl/amine exciplex. Titration with trifluoroacetic acid revealed that, in spite of formally possessing four nitrogen atoms, the cyclam core undergoes only two successive protonation steps which significantly affect the luminescence properties. 

Once formed, the protonated amine groups remain in the aqueous phase until the pH is increased to the point that the proton is removed. At this point the microdomains of amine reform. This accounts for the hysteresis in the titration curves that is shown in Figure 5. 

The potentiometric titration curves of several poly(electrolyte)s, among which PVA and PEI (branched), have been extensively studied by Bloys von Treslong54). He assumes that in the protonation process, the interactions between the various aminic groups present in the macromolecule may result in a charge distribution which, at partial neutralization, is not random. 

Fig. 4. Potentiometric - - and viscosimetric -O- titration curves using HC1 as titrating reagent ( 3 = degree of protonation of residual tertiary amine groups 5 = overall degree of neutralization e = degree of neutralization of quaternary ammonium hydroxide sites) of partially quatemized poly[thio-l-(N,N-dimethyl-aminomethyl)ethylene]...

Fig. 8. Dependence of the fraction of tertiary amine groups in the systems dodecylamine (DDA)-phenyl glycidyl ether (PGE), DDA-DGEBA, and HMD-DGEBA on conversion of amine functionalities. GPC determination DDA-PGE determination of Up and a, by titration HMD-DGEBA epoxide in excess . amine in excess O DDA-DGEBA amine in excess . The curve was calculated for e = 0,41...

The dissociation of the single lysine amino group of iodinated insulin has been studied by Gruen et al. (1959a). (The inclination separated the titration region of phenolic residues from the titration region of the amine group.) No abnormalities were observed. 

The tertiary amine group in meperidine is directly titratable in non-aqueous media. Meperidine hydrochloride is likewise titratable if mercuric acetate is added to tie up the chloride ion. Standard non-aqueous titration techniques are applicable using either visual indicators or potentiometric end point detection. Several such methods for both meperidine and its hydrochloride salt have been published -. . ... 

Figure 1 4F-2 Curves for the titration of 20.00 mL of 0.1000 M alanine with 0.1000 M NaOH and 0.1000 M HCl. Note that the zwitterion is present before any acid or base has been added. Adding acid protonates the carboxylate group with a pK of 2.35. Adding base reacts with the protonated amine group with a pk of 9.89.

This cure cycle was reported by Bell to give essentially complete curing, and was also shown (through chemical titration of the epoxy and amine groups) to be similarly effective in this laboratory ( 5, 2). ... 

Figure 14 Fluorescence enhancement associated to Zn" coordination to 4. Full triangles refer to the spectrofluorimetric titration by standard base in aqueous MeCN of the two-component system 4, plus 1 equiv. of Zn and excess acid the titration profile obtained for a metal-free solution (open-triangles) is reported for comparative purposes. Coordination to Zn", a pH > 4.5, interrupts the eT process from the amine group adjacent to the fluorophore and awakens the fluorescence.

---