Amines acid-base chemistry

Carbon compounds that also contain nitrogen, such as the cimines, play a significant peirt of any Organic 11 course. You encounter more acid-base chemistry with the amines, along with some more reactions. We hit this topic in Chapter 13 and give you some tips for multistep synthesis. 

The effect of temperature on the acid base chemistry of the stationary phase can also play a role in separation. Free silanol groups on the stationary phase may exhibit changes in acid base chemistry with temperature [28]. Also, reverse phase columns with amine, amide, or acidic functional groups will be affected by the interaction of the temperature, the ionization state of the stationary phase, the mobile phase acidity, and the ionization state of the solute. Most non-linear van t Hoff plots can be rationalized in these terms, but it is difficult to predict a priori what the effects will be on a given system. Thus, it is important to characterize the system under study if a simple change in temperature produces unexpected effects. 

The typical preparation of the cyclic boroles from acyclic starting materials usually involves acid base chemistry or transacetalization protocols. 1,3,2-Diazaborolidines, such as 311 and 313, are readily available via the reaction of the corresponding amines 310 and 314 with boron tribromide (BBr3) and boron halide 312 (Scheme 51) <2006JCD3777>. 

Another approach for the preparation of dendrimer-noble metal nanoparticles in toluene is a process driven by acid-base chemistry and ion pairing [35]. At first, palladium nanoparticles are prepared by reducing aqueous K2PdCl4 with sodium borohydride in the presence of G4 dendrimer where the pH of dendrimer solution is adjusted to about 2. The low pH protonates the exterior amines to a greater extent than the less basic interior tertiary amines. Accordingly, Pd2+ binds preferentially to the interior tertiary amines and upon reduction palladium particles form within the dendrimer interior. After the complete reduction, the pH of solutions is adjusted back to about 8.5. Then, these nanocomposites can be quantitatively transported from the aqueous phase into toluene containing 10-20% of dodecanoic acid. The transition is visualized by the color change brown aqueous solution of dendrimer-palladium nanoparticles becomes clear after addition of the acid, while the toluene layer turns brown. 

A second practical reason for choosing to work with ionic chiral auxiliaries is that they are easy to introduce via simple acid-base chemistry, and once the reaction is over, they are similarly easy to remove. The majority of our work has been carried out using ammonium ions as the ionic chiral auxiliaries, first because there are many optically pure amines of known absolute configuration available,... 

Answer Benzocaine, which lacks an aliphatic amino group needed for salt formation, is practically insoluble in water. Protonation of the aromatic amino group in benzocaine results in a salt with a pKa of 2.78, which is too acidic and, therefore, unsuitable for preparation of a parenteral dosage form for injection. Based on the acid-base chemistry principle, an aromatic amino group is a weak base, because its nonbounded elections are delocalized into the aromatic ring. Thus, an aromatic amine salt, such as benzocaine, will not hold onto its proton as tightly as an aliphatic amine salt and, therefore, will readily release the proton when dissolved in water. 

F.A. La Porta, R.T. Santiago, T.C. Ramalho, M.P. Freitas, and E.F.F. Da Cunha, The role of frontier orbitals in acid-base chemistry of organic amines probed by ab initio and chemometric techniques, Int. J. Quantum Chem. no (2010), pp. 2015-2023. 

Chapters 1—10 begin a study of organic compounds by first reviewing the fundamentals of covalent bonding, the shapes of molecules, and acid-base chemistry. The structures and typical reactions of several important classes of organic compounds are then discussed alkanes, alkenes and alkynes, haloalkanes, alcohols and ethers, benzene and its derivatives, and amines, aldehydes, and ketones, and finally carboxylic acids and their derivatives. 

FIGURE 23.5 An amine and a carboxylic acid must undergo acid-base chemistry to give an ammonium salt of the acid. In amino acids, an intramolecular version of the same reaction gives a zwitterion. 

As we saw earlier (Section 17-9), amines also are capable of attacking the carbonyl function. When the carbonyl is that of a carboxylic acid, the product is a carboxylic amide, the last major class of carboxylic acid derivatives. The mechanism is again addition-elimination but is complicated by acid-base chemistry. 

In Chapter 21, we turn to the last simple compound class that will be covered in this course, the amines. Again, polar bonds and acid-base chemistry will play important roles. 

Amines are organic bases whose acid—base chemistry is like that of ammonia. For example, methyl-amine behaves as a Bronsted base because the nonbonded electron pair of the nitrogen atom can accept a proton from an acid such as hydronium ion. When methylamine accepts a proton, the conjugate acid, methyl-ammonium ion, is produced. 

During previous studies, the role of acid/base chemistry of the pigment was not thoroughly explored. The ammonia adsorption study indicates that the surface does have some acidic characteristic towards NH3. Ammonia has a relatively low pKb value in comparison with typically amine additives for polymer systems. As such, any acidic surface on the pigment would have some interaction with the ammonia. A HALS additive may not have the same level of interaction with a pigment surface due to higher pKb values. 

The chemistry of NH2CI involves chlorination, amination, addition, condensation, redox, acid—base, and decomposition reactions. Monochloramine... 

The chemistry of amines ts dominated by the lone pair of electrons on nitrogen, which makes amines both basic and nucleophilic. They react with acids to form acid-base salts, and they react with electrophiles in many of the polar reactions seen in past chapters. Note in the following electrostatic potential map of trimethylamine how the negative (red) region corresponds to the lone-pair of electrons on nitrogen. 

The reaction between a Lewis acid R3M and a Lewis base ER3, usually resulting in the formation of a Lewis acid-base adduct R3M—ER3, is of fundamental interest in main group chemistry. Numerous experiments, in particular reactions of alane and gallane MH3 with amines and phosphines ER3, have been performed [14]. Several general coordination modes, as summarized in Fig. 2, have been identified by X-ray diffraction. 

Scheelite, 25 349-350 Scheelite sorting, 16 626 Scheibel column, 10 777-778 Scheibler filter, 11 364 Schiff base(s), 21 203, 204, 25 100-101 chelating agents, 5 712t reaction with amino acids, 2 567 reaction with aniline, 2 786 thermochromic materials, 6 622-623 Schiff base chemistry, 24 42 Schiff base (reductive amination) method, for covalent ligand immobilization, 6 396t... 

Proposed mechanisms for polycondensations are essentially the same as those proposed in the organic chemistry of smaller molecules. Here, we will briefly consider several examples to illustrate this similarity between reaction mechanisms for small molecules and those forming polymers. For instance, the synthesis of polyamides (nylons) is envisioned as a simple Sn2 type Lewis acid-base reaction, with the Lewis base nucleophilic amine attacking the electron-poor, electrophilic carbonyl site followed by loss of a proton. 

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

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