Simple addition reactions

The most direct method of preparing [Bp3(NH3)] is by gas-phase addition, in which a carefully controlled flow of each of the gaseous reactants is led into a large evacuated flask, where the product deposits as a white powder  

When one reactant is a liquid and the other a gas at room temperature, a different technique is usually followed. In the preparation of [BF3(OEt2)] for instance, the diethylether and boron trifluoride, stored in separate bulbs 

Reactions between liquids or solids are best carried out by mixing solutions of them in a readily removable inert solvent, e.g. 

If at all possible, the presence of a solid reactant should be avoided unless it is one of those reactions in which an otherwise insoluble compound dissolves in the presence of a complexing agent. Many of these reactions occur with no change in valence state, as when silver chloride dissolves in aqueous ammonia  

Solids may dissolve in complexing agents with a change in valence state (so it is debatable whether such reactions should be classified as simple addition). In the case of the dissolution of metallic silver or gold in water in the presence of cyanide ion, the oxygen of the air acts as the oxidizing agent  

As an example, we can represent the synthesis of nickel tungstate as follows  

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The reactions of bare metal ions will be separated into two sections. Simple addition reactions (Section III.A.l) will be discussed first followed by reactions in which the metal ion causes bond disruption in the potential ligand (Section III. A.2). 

Wagner gave a quantitative thermodynamic theory based on a simple addition reaction of type... 

In the absence of such activation, weak nucleophiles, e.g. H2O , may react only very slowly, but strong ones, e.g. CN, do not require such aid. Additions may also be base-catalysed, the base acting by converting the weak nucleophile HY into the stronger one, Y , e.g. HCN - -base— CN. Further, while acids may activate the carbonyl carbon atom to nucleophilic attack, they may simultaneously reduce the effective concentration of the nucleophile, e.g. CN -1- HA — HCN -f-A , RNHj + HA— RNHj -t- A . Many simple addition reactions of carbonyl compounds are thus found to have an optimum pH this can be of great importance for preparative purposes. 

A basic group removes a proton from the P-carbon of the iminium and forms the enamine. This enamine then reacts as a nucleophile towards the aldehyde group of glyceraldehyde 3-phosphate in a simple addition reaction, and the proton necessary for neutralizing the charge is obtained from an appropriately placed amino acid residue. Finally, the iminium ion loses a proton and hydrolysis releases the product from the enzyme. 

A , RNHj + HA— RNH3 -(- A . Many simple addition reactions of carbonyl compounds are thus found to have an optimum pH this can be of great importance for preparative purposes. 

Another simple addition reaction is the hydration of C02 to form the bicarbonate ion. Without catalysis the reaction may require several seconds,4 5 the apparent first-order rate constant being -0.03 s 1 at 25°C. Cells must often hasten die process. The specific catalyst carbonic anhydrase is widespread in its distribution... 

This process is shown schematically in Figure 7. The ethylene part of the feed reacts with chlorine in the liquid phase to produce 1,2-di-chloroethane (EDC) by a simple addition reaction, in the presence of a ferric chloride catalyst (9). Thermal dehydrochlorination, or cracking, of the intermediate EDC then produces the vinyl chloride monomer and by-product HC1 (1). Acetylene is still needed as the other part of the over-all feed, to react with this by-product HC1 and produce VCM as in the all-acetylene route. 

The simple addition reaction in Scheme 19 illustrates how the notation is used. Ester (1) can be dissected into synthons (2), (3) and (4). Synthons for radical precursors (pro-radicals) possess radical sites ( ) A reagent that is an appropriate radical precursor for the cyclohexyl radical, such as cyclohexyl iodide, is the actual equivalent of synthon (2). By nature, alkene acceptors have one site that reacts with a radical ( ) and one adjacent radical site ( ) that is created upon addition of a radical. Ethyl acrylate is a reagent that is equivalent to synthon (3). Atom or group donors are represented as sites that react with radicals ( ) Tributyltin hydride is a reagent equivalent of (4). In practice, such analysis will usually focus on carbon-carbon bond forming reactions and the atom transfer step may be omitted in the notation for simplicity. 

Although the loss of some anionic or other good leaving group is the usual consequence of such reactions at carbon centres, this is not the case when the electrophilic centre is an element such as silicon, sulfur, phosphorus or a transition metal with available d orbitals in the valence shell. In these cases, a simple addition reaction may occur to give a product of increased co-ordination number. This may involve simple reactions such as the addition of an anion to a neutral molecule or more complex processes (Fig. 4-3). 

A new reaction of iV-acyl thiazolidinethione enolates with enolizable aldoxime ethers has been reported to give 2-(thiazolidine-2-thione)-l-azetines 608 with excellent diastereoselectivity (Equation 235) <2003JA3690>. The absence of either a methoxy or a carbonyl group in the 1-azetines indicated a complex mechanism rather than a simple addition reaction. The formation of azetines has been rationalized by combination of the oxime and TiCh to give a highly electrophilic trichlorotitanium iminium intermediate 609, which adds onto enolate 610 to form intermediate 611, which cyclizes to azetidines 612 (Scheme 81). An irreversible elimination of bis-trichlorotitanium oxide provides the ultimate driving force to produce azetines. 

A mixed metal siloxide complex YCu(OSiPh3)4(PMe2Ph) was obtained by a simple addition reaction (Eq. 3) [48], The geometry around the yttrium atom is distorted tetrahedral. The molecule is cleaved in solution by Lewis basic solvents like THF. 

Amines are the most frequent curing agents, and the curing mechanism is determined by a simple addition reaction of active hydrogens of polyamines to epoxy groups. Consequently, the structures of the cured resins are not much different from the ideal structure shown in Fig. 1 a. Some examples of polyamines are shown in Table 2. The structures of the cured resins obtained from DGEBA and stoichiometrically equivalent amounts of polyamines are shown in Fig. 1 a, and differ in the 0 segment. 

Other organic reactions take place between completely uncharged molecules with no dipole moments. One of the old tests for unsaturation was to treat the compound with bromine water. If the brown colour disappeared, the molecule was unsaturated. We don t use tests like these any more (spectroscopy means we don t need to) but the reaction is still an important one. A simple symmetrical alkene combines with symmetrical bromine in a simple addition reaction. 

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