Amides Atomic number

Esters, under appropriate conditions, undergo hydrolysis. This reaction is the reverse of esterification as shown in the equation on page 207. Esters react with aqueous or alcoholic ammonia to form amides. A number of reactions of esters are due to activity of the carbonyl group and the adjacent a-hydrogen atoms. The reaction of esters with Grignard reagents to form ketones or tertiary alcohols, and the various condensations, are examples of this type of reaction. 

The first amide atom is represented as N where i is the number of the amino acid in the chain. 

In guanine, the diversity of chemical bonds (from the point of view of bond orders) is much smaller than the diversity of atoms (from the point of view of atomic numbers). In addition, one can say that the amide chemical group in guanine seems to be nonexistent because the bond order of the C-N bond is too small... 

In Eq. (16 i denotes an atom up to lour non-rotatable bonds away from the proton and is the total number of those atoms. A bond is deRned as non-rotatable if it belongs to a ring, to a. T-system, or to an amide functional group q- is the partial atomic charge of the atom i, and is the 3D distance between the proton j and the atom i. Figure 10.2-5 shows an example of a proton RDF descriptor. 

The conversion of a carbonyl compound by ammonium polysulphide solution into an amide with the same number of carbon atoms is known as the Willgerodt reaction. The procedure has been improved by the addition of about 40 per cent, of dioxan or of pyridine to increase the mutual solubility of the ketone and aqueous ammonium polysulphide the requisite temperature is lowered to about and the yield is generally better. 

The nomenclature (qv) of polyamides is fraught with a variety of systematic, semisystematic, and common naming systems used variously by different sources. In North America the common practice is to call type AB or type AABB polyamides nylon-x or nylon-respectively, where x refers to the number of carbon atoms between the amide nitrogens. For type AABB polyamides, the number of carbon atoms in the diamine is indicated first, followed by the number of carbon atoms in the diacid. For example, the polyamide formed from 6-aminohexanoic acid [60-32-2] is named nylon-6 [25038-54-4], that formed from 1,6-hexanediamine [124-09-4] or hexamethylenediamine and dodecanedioic acid [693-23-2] is called nylon-6,12 [24936-74-1]. In Europe, the common practice is to use the designation "polyamide," often abbreviated PA, instead of "nylon" in the name. Thus, the two examples above become PA-6 and PA-6,12, respectively. PA is the International Union of Pure and AppHed Chemistry (lUPAC) accepted abbreviation for polyamides. 

Addition compounds form with those organics that contain a donor atom, eg, ketonic oxygen, nitrogen, and sulfur. Thus, adducts form with amides, amines, and A/-heterocycles, as well as acid chlorides and ethers. Addition compounds also form with a number of inorganic compounds, eg, POCl (6,120). In many cases, the addition compounds are dimeric, eg, with ethyl acetate, in titanium tetrachloride-rich systems. By using ammonia, a series of amidodichlorides, Ti(NH2) Cl4, is formed (133). 

When hydroxypteridines are considered, it must be borne in mind that these compounds exist principally in the pteridinone forms, containing thermodynamically stable amide functions, and consequently have low reactivity. Their stability towards acid and alkali correlates well with the number of electron-donating groups which apparently redress the deficit of ir-electrons located at the ring nitrogen atoms. Quantitative correlations can be seen in the decomposition studies of various pteridinones (Table 7). These results are consistent with the number of the oxy functions and their site at the pteridine nucleus. The... 

A number of interesting conclusions could be drawn from the screening. For example, the amide hydrogen atom at the second amino acid residue close to the... 

We ve already seen in Sections 20.7 and 21.7 how amines can be prepared by reduction of nitriles and amides with LiAlH4. The two-step sequence of 5 2 displacement with C followed by reduction thus converts an alkyl halide into a primary alkylamine having one more carbon atom. Amide reduction converts carboxylic acids and their derivatives into amines with the same number of carbon atoms. 

When two compounds whose molecules form hydrogen bonds with each other are both dissolved in water, the hydrogen bond between the two molecules is usually greatly weakened or completely removed, because the molecules generally form hydrogen bonds with the water molecules rather than with each other, especially since the water molecules are present in such great numbers. In amides, the oxygen atom is the preferred site of protonation or complexation with water. 

Protonation studies of diphenylphosphinic esters and amides show that Ji>a H i creases upon protonation of the esters but that ypN< h decreases upon protonation of the amides.Values of JpN< ii have been tabulated for a number of compounds. The cyclic aminophosphine (79) has all four Jpxch constants with the same sign, probably positive. Attachment of the proton to an sp carbon atom, as in (80), does not enhance yi>Ncn in fact the reverse occurs. ... 

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