Addends

Compounds with active hydrogen add to the carbonyl group of acetone, often followed by the condensation of another molecule of the addend or loss of water. Hydrogen sulfide forms hexamethyl-l,3,5-trithiane probably through the transitory intermediate thioacetone which readily trimerizes. Hydrogen cyanide forms acetone cyanohydrin [75-86-5] (CH2)2C(OH)CN, which is further processed to methacrylates. Ammonia and hydrogen cyanide give (CH2)2C(NH2)CN [19355-69-2] ix.orn. 6<55i the widely used polymerization initiator, azobisisobutyronitrile [78-67-1] is made (4). 

The principle of this method depends on the formation of a reversible diastereomeric complex between amino acid enantiomers and chiral addends, by coordination to metal, hydrogen bonding, or ion—ion mutual action, in the presence of metal ion if necessary. L-Proline (60), T.-phenylalanine (61),... 

A/- -toluene su1fony1)-T-phenylalanine (62), L-histidine methyl ester (63), A/-acetyl L-valine /-butyl amide (64), etc, are used as chiral addends. 

With a suitable combination of electron-deficient fluoroalkene and electron-rich addend, cycloaddition can proceed by a dipolar mechanism involving zwitte-rion intermediates Like Us isomer, l,2-bis(trifluoromethyl)-l,2-dicyanoethylene [85], l,l-bis(trifluoromethyl)-2,2-dicyanoethylene forms cyclobutanes by an ionic mechanism [104, 105, 106] (equations 39 and 40)... 

Both the carbon-carbon and carbon-oxygen double bonds of fluoroketenes can take part in [2+2] cycloadditions, but with cyclopentadiene, only cyclo butanones are produced via concerted [2 +2 ] additions [J34] (equation 58) Cycloadditions involving the carbon-oxygen double bonds to form oxetanes are discussed on page 855 Difluoroketene is veiy short lived and difficult to intercept but has been trapped successfully by very electron rich addends to give 2 2 di fluorocyclobutanones m moderate yields [/55] (equation 59)... 

Addend, n. something to be added, addendum, addieren, v.t. add. — addierend, p.a. additive. 

Additions include the attachment of two univalent atoms or groups (called addends) to an unsaturated system, e. g., to olefins, carbonyl groups, aromatic systems, carbenes, etc. (Rule 2.1). For example, the addition of hydrocyanic acid to the car-... 

Clearly kinetics alone will not distinguish the two schemes. To gain this distinction one can deliberately add a reagent that, judging from its independent chemistry, will react with one of the possible chain-carrying radicals. If the suspected radical is indeed an intermediate, and it reacts with the addend, the overall reaction will be slowed or halted. The added substance is a chain-breaker. In this case Fe2+ and Cu2+ (separately) were added. The first of these would very likely react with either of the peroxyl radicals, ROO or MOO. Indeed, Fe2+ dramatically inhibits the reaction. This evidence confirms the chain nature of the process, but does not distinguish between the mechanisms since both ROO and MOO would be scavenged by Fe2+. 

The essential difference in chemical behavior of chlorides and bromides used as telogens (addends) can be distinctly seen when the reactions of chloro- and bromoacetates are compared. In addition and telomerization reactions monochloroacetates react with 1-alkenes exclusively at C-H bond [under initiation... 

The easy homolysis of C-Br bond in CBr4 allowed us to conduct the radical chain reaction of CBr4 with 3,3,3-trifluoropropene under common conditions (benzoyl peroxide), although in this case the strong electrophiles are used as reagents (an addend and a monomer), i.e. a very unfavorable combination of polar factors for proceeding the process takes place (ref. 6). 

Table 1. Radical reactions of organobrominc addends with unsaturated compounds...

Addend Monomer Reaction conditions Adducts, telomers / Yield / c Ref. 

Additions. For simple 1,2-additions, the names of both addends are given followed by the suffix addition . The addends are named in order of priority in the Cahn-Ingold-Prelog system (p. 139), the lower ranking addend coming first. Multivalent addition is indicated by biaddition , and so on. 

The second addend in Equation 22.21 considers the energy stored in the substantially strained fragile but soft filler clusters ... 

Methanofullerene 20 with phenylacetylene dendrimer addends has also been reported [45] (Fig. 10). The UV absorption of fullerodendrimer 20 is particularly strong and is mainly attributed to transitions located on the two dendritic branches of the molecule. The photophysical investigations revealed that the large poly(aryl)acetylene branches act as photon antennae [46]. 

The first addend is positive, and measures the direct effect of the rise of the co-payment rate. It expresses the effect of the normative change in the distribution of the financial burden between the two parties, before the user s reaction of restraint in the use of the pharmaceutical is taken into consideration. The other two addends are negative, and quantify the decrease in expenditure caused by the drop in consumption as a reaction to the rise in the price paid. The balance can have either sign, depending on the elasticity of demand and the size of the increase in the co-payment. In the example shown in Figure 7.3, despite a considerable decrease in the quantity consumed, the patient will end up paying more for the drag than before. 

The chain length is therefore adversely afFected by the irradiation dose rate being inversely proportional to its square root. Wagner (1969) lists a large class of unsaturated compounds in which addition reactions can be induced by irradiation. Typical examples involving long chain lengths are for the addends HC1, Cl2, and HBr in ethylene, benzene, toluene, and so on. where the products are telomers or hexachlorides. 

Anyway, the catalysed process is not a clean one, generally also affording five-membered ring 480 and open-chain products 481, as the result of the cyclopropane ring-opening of one or both the methylenecyclopropane addends (Table 37) [116,130,2],... 

Sensitized cross-dimerizations form a second group with a few examples shown in Eqs. 24—27. Most examples involve electron-deficient olefins as one addend. The reactions are again highly regioselective... 

Qualitatively, the interaction diagram would closely resemble that in Fig. 3, since electron-donating substituents in both addends would raise the molecular levels of both the carbonyl compound and the olefin. Only the energy gap, E(n)-> F(n), would increase, the net result being that the calculated ratio of concerted to biradical reaction, Eqs. 40 and 41, should be even closer to unity than in the formaldehyde-ethylene case. Detailed calculations 38> support this conclusion, so PMO theory predicts that the overall stereochemical results are due to a combination of concerted (singlet) and biradical (triplet) mechanisms. This explanation agrees with the experimental facts, and it bypasses the necessity to postulate differential rates of rotation and closure for different kinds of biradical intermediates. 

An important factor that stabilizes the complex or transition state leading to biradical intermediate is the dipole-dipole interaction between the addends. The orientation given in 13 would be more stable than 14 from this factor, but the orientation in 14 is preferred by the orbital... 

In the case of allylpotassium, the metal complex exists as a symmetric n structure. No temperature dependence was shown by either 13C NMR for A5[C(i) —C(3)] or by 1H NMR for substitution with deuterium at Cp). Thompson and Ford measured experimentally a variety of allylalkali metal compounds using variable-temperature NMR in THF-dx45. Addends such as TMEDA, hexamethylphosphoric triamide (HMPA), 15-crown-5-ether, [2.1.1]cryptand and n-butyllithium showed either no change in the spectrum or rapid decomposition of the complexing agent. Measurement of the populations of E (17) and Z (18) isomers of 1-isopropylallylpotassium showed the Z isomer to be more stable (Table 11). 

The synthesis of C60-based dyads in which the Ccm core is covalently attached to a strong electron acceptor moiety, has been carried out by 1,3-dipolar cycloaddition of in situ generated nitrile oxides with C(,o- As expected, the obtained adducts show reduction waves of the fullerene core that are anodically shifted in comparison with the parent Cr>o. This indicates that they are remarkably stronger acceptors than Ceo-The electron acceptor organic addend also undergoes an anodic shift due to the electronic interaction with the C(,o moiety (545). 

N. Qian, Y. Rubin, "Complete Control over Addend Permutation at all Six pseudo-Octahedral Positions of Fullerene Ceo,J. Am Chem Soc 2000,122, in press. 

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