Hexane reactions atmosphere

Demerseman and coworkers studied recently the coupling reaction between an unsaturated alkynetitanium(II) complex and carbon dioxide [84]. The titanium-diphenylacetylene complex (n -C5H5)(n -C5Me5)Ti-(PhC=CPh) adds readily CO2 to give a five-membered metallacyclic compound via carbon-carbon bond formation (Equation 14). This reaction occurs smoothly in hexane under atmospheric pressure and is supported by the well known tendency of titanium to form stable Ti-0 bonds. 

A different kind of shape selectivity is restricted transition state shape selectivity. It is related not to transport restrictions but instead to size restrictions of the catalyst pores, which hinder the fonnation of transition states that are too large to fit thus reactions proceeding tiirough smaller transition states are favoured. The catalytic activities for the cracking of hexanes to give smaller hydrocarbons, measured as first-order rate constants at 811 K and atmospheric pressure, were found to be the following for the reactions catalysed by crystallites of HZSM-5 14 n-... 

Dicobalt octacarbonyl [10210-68-1] M 341.9, m 51 . Orange-brown crystals by recrystn from n-hexane under a carbon monoxide atmosphere [Ojima et al. J Am Chem Soc 109 7714 1987 see also Hileman in Preparative Inorganic Reactions, Jolly Ed. Vol 1 101 1987]. 

To a stirred solution of 2.0 mmol of LDA in 3.3 mL of a 60 40 mixture of THF/hexane at — 78 °C under a nitrogen atmosphere is added 264 mg (2.0 mmol) of tert-butyl propanoatc in 2 mL of THF. After 30 min stirring a solution of 168 mg (1.5 mmol) of ethyl (t)-2-butenoalein 1.5 mL of THE is added and the mixture is stirred for an additional hour at — 78 °C. The reaction is quenched by addition of sat. NH4C1. Extraction with diethyl ether, drying over NiiCl followed by evaporation of the solvent and short path distillation gives the adduct yield 378 mg (1.2 mmol, 84%). 

To a stirred suspension of 2.3 mmol LDA in 20 mL of THF arc added at — 80 X under a nitrogen atmosphere 253 mg (1 mmol) of methyl 2-(2-hydroxy-2,6,6-trimethylbicyclo[3.1.1]hept-3-ylideneamino)propanoate and the mixture is stirred for a further 30 min. After the addition of 114 mg (1 mmol) of ethyl ( )-2-butenoate the mixture is stirred at — 80 °C until the reaction is complete (followed by TLC on silica gel). The mixture is poured into 70 mL of sat. aq NH4C1 and subsequently extracted three times with diethyl ether. The combined ether layers arc dried over Na2S04 and the solvent is evaporated. The crude adduct is purified by chromatography (silica gel. diethyl ether/hexane 66 34) yield 330 mg (90%). 

To a mixture of 1,3-dibromobenzene (4.36 g, 18.49 mmol), 1,3-phenylene diamine 111 (2.00 g, 18.49 mmol), NaO-t-Bu (3.73 g, 38.84 mmol), Pd2(dba)3 (0.339 g, 0.37 mmol), and BINAP (0.691 g, 1.11 mmol) in a heavy-walled flask equipped with a Teflon valve was added THF (15 mL) under inert atmosphere. The flask was sealed and heated to 90°C. After 24 h, die reaction mixture was cooled to room temperature and neutralized using 0.2 mol equivalents of 2.4 N HC1 in MeOH. The polymer was precipitated from hexanes, filtered, and dried under vacuum. The dried polymer was redissolved in THF, filtered through Celite, and reprecipitated. The solid was collected by filtration and dien purified by Soxlilet extraction with CH2C12 overnight. After drying under vacuum, a green-tan solid was obtain in 106% yield. GPC (NMP, polystyrene standards) Mw = 39,000 ... 

The triethoxysilapropylisocyanide was prepared as outlined in reference 7, and characterized by its lH, 13C NMR, IR and mass spectra. For details see reference 1A. Aqueous NaOH [0.09 g in 3 ml H2O] was added dropwise to a mixture of 30 ml [0.17 mole] of (Et0)2SiMe2 and 2.5 ml [0.01 mole] of (EtO)3Si(CH2)3NC. The solution was stirred under an inert atmosphere for 2A hr. in the dark at room temperature. After completion of the reaction, the residue was washed thoroughly with water until neutral. It was then resuspended in hexane and dried over MgSO for several hours. The solution was decanted, the... 

This reactive liquid is now normally supplied commercially as a solution (up to 25 wt.%) in pentane, hexane or heptane, because it reacts with ether and ethereal solutions must be stored under refrigeration. Reaction with atmospheric oxygen or... 

The reaction is complete when the clear supernatant solution in the reaction vessel no longer contains chlorine as detected by the addition of dilute nitric acid and silver nitrate solution to ca. 1-ml. of the clear solution withdrawn from the reaction flask. After the reaction is complete, the ice bath is removed, and stirring is continued for 2 hours at room temperature. After standing overnight, the dimethylammonium chloride is filtered and washed with n-hexane, with careful exclusion of the moisture of the atmosphere. The combined filtrates are distilled at atmospheric pressure to remove the solvent. The tris(dimethylamino)arsine distills at 36°/2 mm. (55 to 57°/10 mm.). The yield is 402 g. (78%). 

A mixture of diethyl 2-bromo-l-phenylethenylphosphonite (30.3 g, 0.1 mol) and dimethyl maleate (14.4 g, 0.1 mol) was stirred for 4 h at room temperature under an argon atmosphere. At this time, hexane was added to the reaction mixture sufficient for complete precipitation, and the resultant crystals (unreacted dimethyl maleate) were removed by filtration. The oily residue was treated on a silica gel column (40/100 pm) using a pentane/acetone (8 2) mixture, allowing the elution and isolation after evaporation of pure l-ethoxy-2-phenyl-4,5-dimetho x yea rb o n y I - A2-X5-phospholene 1-oxide (8.9 g, 27%), which exhibited spectra and analytical data in accord with the proposed structure. 

Preparation of 4-12-cvclohexenvloxv )-stvrene. A stirred mixture of 34.36g (0.096 mole) methyltriphenylphosphonium bromide and 10.75g (0.096 mole) potassium t-butoxide in 200ml dry THF is treated drop-wise with a solution of 16.16g (0.080 mole) of 4-(2-cyclohexenyl)-benzaldehyde in 30ml THF under inert atmosphere. Once the addition of aldehyde was completed, the mixture was stirred at room temperature for another 2 hours. Ether and water were then added to the reaction mixture until clearly separated phases were obtained with no solid residue. The organic layer was separated and washed three times with water, dried over magnesium sulfate and evaporated. The resulting semi-solid was triturated in 10% ethyl acetate-hexane mixture to remove most of the triphenylphosphine and the evaporated extract was purified by preparative HPLC using hexane as eluent. This afforded 9.35g (58%) of the pure monomer, which was fully characterized by H and C-NMR as well as mass spectrometry. 

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