2- Butyne, 715 table

The authors noticed that polylithiated phenylallenes have a vibrational behaviour similar to that of polylithiated propynes and butynes (Table 8) . The monolithium compounds from terminal acetylenes were found to have acetylenic structures (2050 cm ), whereas the monolithium derivatives of non-terminal acetylenes could exist in either acetylenic (2000 cm ) or allenic (1870-1850 cm ) forms (Table 8) °. The polylithium... 

The solvolysis of 3-haIo-3-alkyl-l-butynes (Table 6) is very slow as compared to the solvolysis of /-alkyl halides, but is strongly accelerated by base. Under these conditions the reactions are first-order in both halide and base concentrations, and proceed predominantly with displacement of the halogen (only 3% elimination was found under basic conditions, as compared to 35% in the neutral solvolysis) . 

Butynediol. Butynediol, 2-butyne-l,4-diol, [110-65-6] was first synthesized in 1906 by reaction of acetylene bis(magnesium bromide) with paraformaldehyde (43). It is available commercially as a crystalline soHd or a 35% aqueous solution manufactured by ethynylation of formaldehyde. Physical properties are Hsted in Table 2. 

Figure 9 Table comparing the activity of the E and Z olefin and butyne analogues of WIN54954.

Transition-metal catalyzed decomposition of alkyl diazoacetates in the presence of acetylenes offers direct access to cyclopropene carboxylates 224 in some cases, the bicyclobutane derivatives 225 were isolated as minor by-products. It seems justified to state that the traditional copper catalysts have been superseded meanwhile by Rh2(OAc)4, because of higher yields and milder reaction conditions217,218) (Table 17). [(n3-C3H5)PdCl]2 has been shown to promote cyclopropenation of 2-butyne with ethyl diazoacetate under very mild conditions, too 2l9), but obviously, this variant did not achieve general usage. Moreover, Rh2(OAc)4 proved to be the much more efficient catalyst in this special case (see Table 17). 

Recently, Chaudhari compared the activity of dispersed nanosized metal particles prepared by chemical or radiolytic reduction and stabilized by various polymers (PVP, PVA or poly(methylvinyl ether)) with the one of conventional supported metal catalysts in the partial hydrogenation of 2-butyne-l,4-diol. Several transition metals (e.g., Pd, Pt, Rh, Ru, Ni) were prepared according to conventional methods and subsequently investigated [89]. In general, the catalysts prepared by chemical reduction methods were more active than those prepared by radiolysis, and in all cases aqueous colloids showed a higher catalytic activity (up to 40-fold) in comparison with corresponding conventional catalysts. The best results were obtained with cubic Pd nanosized particles obtained by chemical reduction (Table 9.13). 

Table 9.13 Comparison of colloidal and heterogeneous catalysts in the hydrogenation of 2-butyne-l,4-diol. (Adapted from [89])...

In contrast, when l-bromo-2-butyne is employed in this sequence, allenylcarbi-nols are the major adducts (Table 9.63). In the former case, the allenyl antimony reagent is presumed to prevail whereas in the latter sequence, the terminal Me substituent causes the equilibrium to shift toward the sterically favored propargylic isomer. 

Table 2.3-2. Co-oligomaization of a 2 1 mixture of butadiene and 2-butyne at 40 °C by Ni-, Grand Ti-catalysts (the product yields (%) are based on alkyne)...

The only significant loss of alkynes is reaction with OH, for which a pressure dependence is observed. Table 6.15 gives the high-pressure limiting rate constants for the OH reactions with acetylene, propyne, 1-butyne, and 2-butyne. The reaction of acetylene approaches the high-pressure limit at several thousand Torr (see Problem 5). However, for the larger alkynes, the reactions are essentially at the high-pressure limit at 1 atm (and room temperature). 

The magnitude of the rate constants, their observed pressure dependence, and the products of the reactions are consistent with the mechanism involving the initial addition of OH to the triple bond. For example, the OH-l-butyne reaction at 298 K is about a factor of three faster than the reaction with n-butane (see Table 6.2), despite the fact that it has fewer abstractable hydrogens and the = C — H bond is much stronger than a primary -C-H bond ( 125 vs 100 kcal mol -1). In addition, a pressure dependence is not consistent with a simple hydrogen atom abstraction (see Chapter 5.A.2). 

Table X, however, shows clearly that, in contrast to the butadiene-ethylene system, triphenylphosphine is the most successful ligand. We will return to this point later. The preparation of DMCDeT on a laboratory scale can be conveniently carried out by dissolving the nickel-ligand catalyst [which may be prepared by reduction of nickel acetylacetonate or directly from bis(cyclooctadiene)nickel and triphenylphosphine] in a solution of butadiene in toluene. Butyne is then added to give a butadiene-to-butyne ratio of 5-10 1. The reaction is conducted at 20° C and the contraction in volume is observed. The reaction is terminated at the break in the contraction curve (Fig. 3).

The [2+2] cycloaddition reactions of various 4-dialkylamino-3-butyn-2-ones with substituted phenyl isothiocyanates in refluxing tetrahydrofuran gave access to a series of thietimines 92a-j in poor to satisfactory yields (Table 6) <2001SL361>. As it may be concluded from Table 6, when diethylamine derivatives were replaced by dimethylamine... 

Table 6 [2+2] Cycloadditions of 4-dialkylamino-3-butyn-2-ones with phenyl isothiocyanates...

A mononuclear tantalum-benzyne complex (121) has been prepared by thermolysis of 120 [Eq. (20)].14 An X-ray crystal structure was reported for 121. Bond lengths for the benzyne unit are given in Table III. Complex 121 exhibits a rich insertion chemistry similar to that of Ti, Zr, and Ru benzyne complexes. Insertion reactions of 121 with ethylene, 2-butyne, acetonitrile, and carbon dioxide give 122, 123, 124, and 125, respectively (Scheme 15). Diphenylacetylene does not couple with 121, presumably because of steric constraints. Reagents with acidic protons such as methanol or terminal alkynes cleave the Ta—C bond to give butyl isocyanide and carbon monoxide, but... 

The only complex in Table I with identical ligands in the two positions cis to the alkyne is the [(775-C9H7)MoL2(MeC=CMe]+ cation with L = PMe3 (72). Here the 2-butyne is parallel to one Mo—L vector and perpendicular to one Mo—L vector (Fig. 11). The 7r-ligand properties of the PMe3 ligands are probably not sufficiently dominant to create a substantial alkyne preference between the dir orbital combinations which are available. 

Limited electrochemical data for Mo(CO)(RC=CR)L2X2 complexes indicate a reversible reduction at -1.18 V versus SSCE for four 2-butyne derivatives while the one phenylacetylene complex studied exhibited a reversible reduction at -1.00 V (Table IX). These results are consistent with the model developed for Mo(CO)(RC=CR)(S2CNEt2)2 in that the more electron-rich dialkylalkyne would be expected to push the LUMO to higher energy than PhC=CH. These same complexes were characterized by an irreversible oxidation around +0.9 V (46). A preliminary report that [CpMo[P(OMe)3]2(MeC=CMe)]+ undergoes a reversible one-electron reduction at -1.04 V versus SSCE has been used to support the possibility of odd-electron species as reactive intermediates in this system (74). 

The physical properties of alkynes (Table 9-2) are similar to those of alkanes and alkenes of similar molecular weights. Alkynes are relatively nonpolar and nearly insoluble in water. They are quite soluble in most organic solvents, including acetone, ether, methylene chloride, chloroform, and alcohols. Many alkynes have characteristic, mildly offensive odors. Ethyne, propyne, and the butynes are gases at room temperature, just... 

Butadiene and HC1 (4 of Table 5) yield a mixture of trans and cis chloro-2-butene together with considerable amounts of 2-butyne which, in turn, adds HC1 much more slowly than the parent isomer. The orientation is that predicted following equation (11) and indicates the intermediacy of a vinyl cation. 

Cycloadditions [40] Perfluoro-2-butyne is a highly reactive dienophUe and many [4 + 2] cycloaddition and 1,3-dipolar addition reactions involving this alkyne have been reported (Table 7.20). Moreover, [2 + 2] additions with hydrocarbon alkenes are possible (Table 7.20). 

Table 7.20 Cycloaddition reactions with perfluoro-2-butyne...

Other systems Additions of perfluoro-2-butyne [143] and acetylene dicarboxylic ester [139] to perfluoro-aromatics will also occur (see Table 9.9 and Chapter 7, Section lllB). The extending anion may be trapped, and the more reactive the aromatic compound used, the more effective the competition with polymer formation (Figure 9.57) [144]. 

For example, the treatment of l,4-dichloro-2-butyne with sodium hydroxide results in diacetylene (HC=C—C CH) in good yield (see Table 4, entry 39). 

The preparation of cyclopropcnes from diazo compounds and alkynes has been reviewed. - A generalized reaction is shown. Further examples are given in Table 4. The use of a flow reactor can increase yields in the thermal conversion of ethyl diazoacetate and butyne into the cyclopropenc." - ... 

The gas phase study involved also the deuteration of 1-butyne. Deuterium was distributed in the major product and reactant as shown in Table XXX. Analysis of the 1-butene by NMR showed that no deut-... 

Property data from the literature (1-55,84-93) are given in Table 3-1. Critical constants have been determined experimentally for acetylene and methylacetylene (1-7). Critical pressure and volume are estimated for 1 butyne and 2 butyne (5). Additional property data such as acentric factor, enthalpy of formation, lower explosion limit in air and solubility in water are also available. The DIPPR (Design Institute for Physical Property Research) project (5) and recent data compilations by Yaws and co-workers (44-55) were consulted extensively in preparing the tabulation. 

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