Interactions, amine-carbonyl

Amines (Lewis bases) react with carbonyl groups (Lewis acids) by carbonyl addition reactions. Indeed, a substantial fraction of organic chemistry is concerned with carbonyl addition reactions of which this is a typical example. What we wish to discuss here is both their interaction and also their reaction. What, exactly, happens when these two groups come together, and how do they interact or react  

Let us consider the general problem of the reaction coordinate diagram of this reaction. As a simple example, consider the reaction with ammonia and formaldehyde [Reaction (1)]  

It is known that in such a reaction, the ammonia attacks the carbonyl carbon of the formaldehyde by coming in with its electrons pointing toward the carbon, and approximately perpendicular to the plane of the carbonyl systan, as shown in Structure 5  

The geometry of the initial carbonyl system is trigonal, planar, and approximately sp hybridized at carbon. The addition product shown for Reaction 1 wonld be approximately tetrahedral and sp hybridized. 

If one wishes to stndy a reaction theoretically, the most simple example is usually where one starts, which wonld be with the ammonia/formaldehyde reaction in the present case. Bnt when stndying a reaction experimentally, it is often convenient to start with much more complicated examples. The latter approach was followed historically, and we will discnss it here in historical order. 

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The only thing about which the crystallographic study did not provide much information was the energy of the amine-carbonyl interaction. This is a problem that is well suited to investigation by ab initio calculations. We can easily calculate the reaction coordinate for carbonyl additions between simple molecules, and simultaneously obtain the energy of the system as a function of distance and orientation between the molecules. 

Typical functional groups which are capable of polar interactions include hydroxyls, amines, carbonyls and groups containing heteroatoms such as... 

Figure 6.11 Co-crystal structure of LY294002 bound to PI3K-y. The binding mode mimics that of ATP. Thus, the morpholine oxygen forms the hinge region interaction with the backbone amine of Val-882 (compare the pyrimidine nitrogen in ATP) and the carbonyl interacts with Lys-833 (compare the phosphate in ATP).

Undoubtedly, the products of these primary biochemical events, i.e., fatty and other acids, peptides, and amino adds, contribute to cheese flavor, perhaps very significantly in many varieties and proteolysis certainly has a major influence on the various rheological properties of cheese, e.g., texture, meltability, and stretchability. However, the finer points of cheese flavor are almost certainly due to further modification of the products of the primary reactions. The most clear-cut example of this is the oxidation of fatty acids to methyl ketones in blue cheeses. Catabolism of amino acids leads to the production of numerous sapid compounds, including amines, carbonyls, acids, thiols, and alcohols. Many of these compounds may interact chemically with each other and the compounds of other reactions via the Maillard and Strecker reactions. At present, relatively little is known concerning the enzymology of amino acid catabolism in most cheeses and even less is known about the chemical reactions. It is very likely that research attention will focus on these secondary and tertiary reactions in the short-term future. 

The mode and orientations of interaction of urea molecules with these surfaces are shown in Figure 8.1. The urea moiety prefers to interact with both the potassium and chloride ions in 100 and 110 surfaces. The carbonyl oxygen of urea interacts with the potassium ion, whereas the hydrogen of amine functionality interacts with the chloride ion. In the case of the 111 surface of KCl, the carbonyl oxygen interacts with the potassium ion. 

The methods of preparation of ferrocene have been reviewed by Pauson and by Fischer. Ferrocene has been made by the reaction of ferric chloride with cyclopentadienylmagnesium bromide, by the direct thermal reaction of cyclopentadiene with iron metal, by the direct interaction of cyclopentadiene with iron carbonyl, by the reaction of ferrous chloride with cyclopentadiene in the presence of organic bases such as diethyl-amine, by the reaction of ferrous chloride with sodium cyclo-[lentadienide in liquid ammonia, and from cyclopentadiene and... 

The heavier chalcogens are more prone towards secondary interactions than sulfur. In particular, the chemistry of tellurium has numerous examples of intramolecular coordination in derivatives such as diazenes, Schiff bases, pyridines, amines, and carbonylic compounds. The oxidation state of the chalcogen is also influential sulfur(IV) centres engender stronger interactions than sulfur(II). For example, the thiazocine derivative 15.9 displays a S N distance that is markedly longer than that in the corresponding sulfoxide 15.10 (2.97 A V5. 2.75-2.83 A, respectively). ... 

In the case of nonionic but polar compounds such as sugars, the excellent solvent properties of water stem from its ability to readily form hydrogen bonds with the polar functional groups on these compounds, such as hydroxyls, amines, and carbonyls. These polar interactions between solvent and solute are stronger than the intermolecular attractions between solute molecules caused by van der Waals forces and weaker hydrogen bonding. Thus, the solute molecules readily dissolve in water. 

Transition-state stabilization in chymotrypsin also involves the side chains of the substrate. The side chain of the departing amine product forms stronger interactions with the enzyme upon formation of the tetrahedral intermediate. When the tetrahedral intermediate breaks down (Figure 16.24d and e), steric repulsion between the product amine group and the carbonyl group of the acyl-enzyme intermediate leads to departure of the amine product. 

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