Butadiene yields

Spectroscopically determined values of P vai y, but they aie usually around —2.4 eV. In the section on resonance stabilization, we saw that thermodynamic measurements of the total resonance stabilization of butadiene yield 11 and 29 kJ mol according to the reference standard chosen. Calculate the delocalization energy of buta-1,3-diene in units of p. Determine two values for the size of the energy unit p from the thermochemical estimates given. Do these agree well or poorly with the spectroscopic values ... 

Thermal electrocyclizations of perhalogenated 1,3-butadienes yield perhalogenated cyclobutenes which can be solvolysed to 3,4-dihydroxy-3-cydobutene-l,2-dione ( squaric acid") and its derivatives (G. Maahs, 1966 H. Knorr, 1978 A.H. Schmidt, 1978). Double CO extrusion from fused cyclobutenediones has been used to produce cycloalkynes, e.g., benzyne from benzocyclobutenedione by irradiation in an argon matrix (O.L. Chapman, 1973) and cyc/o-Ci8, cyclo-Cn, etc. by laser desorption mass spectroscopy of appropriate precursors (see section 4.9.8). 

A"-Octadienylatiori, rather than 0-octadienylation, of aldehyde oximes takes place to give the nitrone 37 as an intermediate, which undergoes 1.3-dipolar addition to butadiene, yielding the isoxazolidine 38[39],... 

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

Butadiene yields ranging from 2 to 7 weight percent on feed (usually 4 to 5j are expected in the steam cracking of naphthas and gas oils. This is generally 35 to 45 percent of the total yield of C4 s. 

All streams leaving the extractive distillation sections are water washed to remove entrained ACN, and the ACN is recovered by distillation. Spent Cj s from the first stage distillation tower overhead may be recycled to a steam cracking unit. This material gives excellent butadiene yields. 

Propane cracking is similar to ethane except for the furnace temperature, which is relatively lower (longer chain hydrocarbons crack easier). However, more by-products are formed than with ethane, and the separation section is more complex. Propane gives lower ethylene yield, higher propylene and butadiene yields, and significantly more aromatic pyrolysis gasoline. Residual gas (mainly H2 and methane) is about two and half times that produced when ethane is used. Increasing the severity... 

Electrophilic addition of Br2 to isoprene (2-methyl-l,3-butadiene) yields the following product mixture ... 

Reaction of [Ir(coe)(N(SiMe3CH2PPh2)2] with excess 1,3-butadiene yields the structurally characterized, five-coordinate complex [Ir(C4H6)[N(SiMe2CH2PPh2)2], which contains the P2N ligand coordinated in a quasi-facial manner, and the 1,3-butadiene bound in a s-cis-ri4-tt mode.691... 

The photosensitized dimerization of isoprene is considerably more complex than that of butadiene, yielding cyclobutanes (14)—(16) as well as four dimers of noncyclobutane types<9 11,18) ... 

With l,l-difluoro-2,2-dichloroethylene, butadiene yielded cyclobutane (31) in the presence of benzophenone ... 

The products of electrochemical oxidation of conjugated dienes are considerably affected by the reaction conditions such as the material of the electrode, the supporting electrolyte and the solvent. The oxidation of butadiene with a graphite or carbon-cloth anode in 0.5 M methanolic solution of NaClCU mainly yields dimerized products along with small amounts of monomeric and trimeric compounds (equation 5)1. The use of platinum or glassy carbon mainly gives monomeric products. Other dienes such as isoprene, 1,3-cyclohexadiene, 2,4-hexadiene, 1,3-pentadiene and 2,3-dimethyl-l,3-butadiene yield complex mixtures of isomers of monomeric, dimeric and trimeric compounds, in which the dimeric products are the main products. 

Other conjugated diene systems readily react with either H4Ru4-(CO)i2 or Ru3(CO)i2, to yield 7r-allyl complexes. Thus, butadiene yields the crotyl derivative HRu3(CO)9C4H5. The X-ray structure of the related adduct formed from cis-trans- or trans-trans-2,4-diene is shown in Fig. 12. The hydride is considered to bond to the Ru(l)-Ru(2) edge, as this is the longest metal-metal bond in the structure and in the... 

The addition of deuterium to 1,3-butadiene yields mainly 1-butene and isotopic distribution in these products is nearly identical and 70% of the initial product corresponds to simple 1,2 or 1,4 addition. Meyer and Burwell suggest that 1,3-butadiene is adsorbed on the surface in the trans conformation. Addition of deuterium to a terminal earbon atom produces an allylic species which is a common intermediate for the formation of both major products, I-butene and trans-2-butene. 

The method described, which is the only one available for the direct preparation of 1,1,3-trichloroalkanes, is applicable to aliphatic olefins and gives good yields, especially with terminal olefins. With styrene or butadiene, yields are much lower. 

Decrease butadiene yield while increasing potential alkylate feed. Unlike increasing riser top temperature, ZSM-5 does not increase butadiene yield with increasing octane (Table XII) fl2-14 ). Butadiene make can negatively impact and ultimately limit downstream alkylation capacity. Thus, G and G. products from ZSM-5 can produce more alkylate product at the same effective alkylation unit capacity. 

One of the polymerization routes involves polymerization of one or the other of the double bounds in the usual manner. The other route involves the two double bonds acting in a unique and concerted manner. Thus addition of an initiating radical to a 1,3-diene such as 1,3-butadiene yields an allylic radical with the two equivalent resonance forms LI and LII... 

Butadiene and Isoprene. Butane may be transformed directly to 1,3-buta-diene on chromia-alumina (Houdry Catadiene process).144-146 172 The most significant condition is operation under subatmospheric pressure (0.1-0.4 atm), which provides an improved yield of 1,3-butadiene. Operating at about 600°C, the process produces a mixture of butenes and 1,3-butadiene. After the removal of the latter, the remaining butane-butenes mixture is mixed with fresh butane and recycled. Extensive coke formation requires regeneration of the catalyst after a few minutes of operation. 1,3-Butadiene yields up to 63% are obtained at a conversion level of 30 40%. 

Much higher butadiene yields may be obtained in a two-step process developed by Phillips in which butane is first converted to butenes with the chromia-alumina catalyst, and the butenes are then further dehydrogenated to 1,3-butadiene.144 173 The butene selectivity in the first step is about 80-85% (600°C, atmospheric pressure). The butenes recovered from the reaction mixture undergo further dehydrogenation in the presence of excess steam (10-20 mol) over a mixed... 

Pure V205 was investigated by Ai [9] using a flow reactor at 350°C. A maximum butadiene yield of 46% is reported, while furan and maleic acid anhydride can be produced (from butadiene and furan) with maximum selectivities of 72 and 60%, respectively. The depth of oxidation can be controlled by the oxygen pressure and the contact time. Isomerization reactions do not occur. Crotonaldehyde is formed as a by-product. The... 

This phenomenological description can be used to rationalize the difference between a- and y-Fe203 (18). As shown in Table VI, the butadiene yield... 

The Cope rearrangement produces a number of interesting phenomena in ring systems. Thermal dimerization of butadiene yields as one product 1,5-cyclooctadiene (Equation 12.104). Formally, this dimerization is a 4 + 4 cycloaddition its actual course (Equation 12.105) is a 2 + 2 addition (presumably biradical) followed by a [3,3]-rearrangement of the eij-divinylcyclo-butane.171... 

Photosensitized dienes dimerize to give 2 + 2 and 2 + 4 addition products. For example, triplet butadiene yields the three products in Equation 13.60,... 

Irradiation of 2-cyanonaphthalene in the presence of 2,3-dimethyl-1,3-butadiene yielded (4 + 4) cycloadducts (70, 71) onto the naphthalene ring (Scheme 25). The main product from the reaction of 2-cyanonaphthalene with cyclohexa-1,3-diene is the (2 + 2) adduct (72), whereas a minor product is the (4 + 4) adduct (73). The reaction with 2,5-dimethyl-2,4-hexadiene leads again to a (2 + 2) cycloadduct (74) and aminoketone (75). 

Nitro-3-phenylisoxazoles 7 (R = H or C02Et) function as dienophiles towards 2,3-dimethyl-butadiene, yielding 8 (94JOC6840, 95T7085). 

Cp ZrCl3] reacts with [Mg(anthracene)(THF)3] to yield the [r 4-anthracene)Cp ZrCl2] anion complex 54 (with [Mg2(p-C1)3(THF)6]+ countercation).56 Treatment of [CpZrCl(dmpe)2] with butadiene yields [CpZrCl(,s-cz, s-r 4-butadiene)(dmpe)] (55).57 Subsequent reaction of such systems (M = Zr, Hf) with hydride ( Red-Al ) leads to [CpM(H) (butadiene)(dmpe)] (56), which rapidly insert terminal alkenes to give the corresponding [CpM(-CI 12C I I2R)(.s-cu-r 4-bmadiene)(dmpe)] systems58 (Scheme 18). 

A study on the homo- and copolymerization of a variety of dienes such as 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, E-l,3-pentadiene, E-l,3-hexadiene, E-l,3-heptadiene, E-l,3-octadiene, E,E-2,4-hexadiene, E-2-methyl-l,3-pentadiene, 1,3-cyclohexadiene mainly focused on mechanistic aspects [139]. It was shown that 1,4-disubstituted butadienes yield frans-1,4-polymers, whereas 2,3-disubstituted butadienes mainly resulted in cis- 1,4-polymers. Polymers obtained by the polymerization of 1,3-disubstituted butadienes showed a mixed trans-1,4/cis-1,4 structure (60/40). The microstructures of the investigated polymers are summarized in Table 26. 

More interesting were the results obtained in reactions of 99 with acyclic dienes catalyzed by Eu(fod)3 (-20°C) and TiCl4 (-78°C). The resulting adducts 100 are unstable and underwent spontaneous sulfinyl elimination at room temperature, affording cyclohexadienes. Reactions with dienes lacking substituents at C-1 (butadiene, 2-methyl butadiene and 2,3-dimethyl butadiene) yielded optically pure compounds 101 (Scheme 49). These results indicate that the regio-selectivity and the 7r-facial selectivity of the cycloadditions are complete (only one adduct is formed) under both catalytic conditions. Desulfinylation of 100 is also completely regioselective. 

Table Z2 lists the pyrolysis product yields for diffinent feedstocks treated at very high severity with recyde of the ethane produced or unconverted at the inlet of the reaction section. Indeed, ethane is an ideal raw material the formation of the lower olefins. It may be observed that the relative production of ethylene decreases as the feedstodc becomes heavier. Also worth noting is that the ratio of Uie ethylene and propylene yidds (C2/CJ ratio) decreases steadily from ethane to the gas oils, whereas the percentage of pyrolysis gasoline (Cs 200 C cot) increases simnltaneously. As to the butadiene yield, thb varies slightly with the type of feedstock in the treatment of liquid petroleum fractions.

Comparison of the 1,3-dienes in both columns of Scheme 39 shows that 1,3-butadiene is the least reactive compound, whereas all other 1,3-dienes in this scheme show similar reactivity. This behavior reflects the fact that 1,3-butadiene yields a terminally monoalkylated allyl cation whereas the other dienes give terminally dialkylated allyl cations (cf., Section III.B.l., Scheme 17). The additional methyl group in the central allylic position, which is present in the allyl cation generated from 2,3-dimethylbutadiene, does not contribute to the stabilization. 

Conjugated dienes also undergo electrophilic additinn reactions readily. but miaturoa of products are invariably obtained. For example, additvm of H0r to 1,3-butadiene yields a mixture of two product tnot counting cis trans ioovnere). 3-Bronvtt-l-butene is the typical Markovnikov product of It i addition, but l-bromo<2 butene app ears unusual. The double bond in this product has moved to a position b ween carbons 2 and 3, and HBr has added to carbons 1 and 4, a residt described as 1.4 addition. 

Butadiene yield increases if nitrogen is used instead of pyrolysis gas due to suppression of secondary and ternary reactions... 

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