4-/-Butylcatechol

A values have been obtained for oxidation of benzenediols by [Fe(bipy)(CN)4], including the effect of pH, i.e., of protonation of the iron(III) complex, and the kinetics of [Fe(phen)(CN)4] oxidation of catechol and of 4-butylcatechol reported. Redox potentials of [Fe(bipy)2(CFQ7] and of [Fe(bipy)(CN)4] are available. The self-exchange rate constant for [Fe(phen)2(CN)2] has been estimated from kinetic data for electron transfer reactions involving, inter alios, catechol and hydroquinone as 2.8 2.5 x 10 dm moF s (in dimethyl sulfoxide). 

Catechol is produced by coproduction with hydroquinone starting from phenol. Other techniques such as coal extraction remain marginal. The installed capacities (- 25,000 t/yr) are now sufficient to cover the demand. Catechol is mainly used for synthesis in food, pharmaceutical, or agrochemical ingredients. A specific appHcation of / fZ-butylcatechol is as a polymerisation inhibitor. 

Toluhydroquinone and methyl / fX butyUiydroquinone provide improved resin color retention 2,5-di-/-butyIhydroquinone also moderates the cure rate of the resin. Quaternary ammonium compounds, such as benzyl trimethyl ammonium hydroxide, are effective stabilizers in combination with hydroquinones and also produce beneficial improvements in color when promoted with cobalt octoate. Copper naphthenate is an active stabilizer at levels of 10 ppm at higher levels (150 ppm) it infiuences the cure rate. Tertiary butylcatechol (TBC) is a popular stabilizer used by fabricators to adjust room temperature gelation characteristics. 

Butadiene reacts readily with oxygen to form polymeric peroxides, which are not very soluble in Hquid butadiene and tend to setde at the bottom of the container because of their higher density. The peroxides are shock sensitive therefore it is imperative to exclude any source of oxygen from butadiene. Addition of antioxidants like /-butylcatechol (TBC) or butylated hydroxy toluene (BHT) removes free radicals that can cause rapid exothermic polymerizations. Butadiene shipments now routinely contain about 100 ppm TBC. Before use, the inhibitor can easily be removed (247,248). Inert gas, such as nitrogen, can also be used to blanket contained butadiene (249). 

Uninhibited chloroprene suitable for polymerisation must be stored at low temperature (<10° C) under nitrogen if quaUty is to be maintained. Otherwise, dimers or oxidation products are formed and polymerisation activity is unpredictable. Insoluble, autocatalytic "popcorn" polymer can also be formed at ambient or higher temperature without adequate inhibition. For longer term storage, inhibition is required. Phenothiasine [92-84-2] / fZ-butylcatechol [2743-78-17, picric acid [88-89-17, and the ammonium salt of /V-nitroso-/V-pheny1hydroxy1 amine [135-20-6] have been recommended. 

Because nitrile rubber is an unsaturated copolymer it is sensitive to oxidative attack and addition of an antioxidant is necessary. The most common practice is to add an emulsion or dispersion of antioxidant or stabilizer to the latex before coagulation. This is sometimes done batchwise to the latex in the blend tank, and sometimes is added continuously to the latex as it is pumped toward further processing. PhenoHc, amine, and organic phosphite materials are used. Examples are di-Z fZ-butylcatechol, octylated diphenylamine, and tris(nonylphenyl) phosphite [26523-78-4]. All are meant to protect the product from oxidation during drying at elevated temperature and during storage until final use. Most mbber processors add additional antioxidant to their compounds when the NBR is mixed with fillers and curatives in order to extend the life of the final mbber part. 

Acetoxy-1,3-butadiene (1,3-butadienyl acetate) cis-trans mixture [1515-76-0] M 112.1, b 42-43 /16mm, 51-52 /20mm, 60-61 /40mm, d 4 0.9466, n g 1.4622. The commercial sample is stabilised with 0.1% of p-/er/-butylcatechol. If the material contains crotonaldehyde (by IR, used in its synthesis) it should be dissolved in Et20, shaken with 40% aqueous sodium bisulfite, then 5% aqueous... 

Methacrylonitrile [126-98-7] M 67.1, b 90.3 , d 0.800, n 1.4007, n 1.3954. Washed (to remove inhibitors such as p-rcrt-butylcatechol) with satd aq NaHS03, 1% NaOH in saturated NaCl and then with saturated NaCl. Dried with CaCl2 and fractionally distd under nitrogen to separate from impurities such as methacrolein and acetone. 

Styrene is difficult to purify and keep pure. Usually contains added inhibitors (such as a trace of hydroquinone). Washed with aqueous NaOH to remove inhibitors (e.g. rert-butanol), then with water, dried for several hours with MgS04 and distd at 25° under reduced pressure in the presence of an inhibitor (such as 0.005% p-tert-butylcatechol). It can be stored at -78°. It can also be stored and kept anhydrous with Linde type 5A molecular sieves, CaH2, CaS04, BaO or sodium, being fractionally distd, and distd in a vacuum line just before use. Alternatively styrene (and its deuterated derivative) were passed through a neutral alumina column before use [Woon et al. J Am Chem Soc 108 7990 1986 Collman J Am Chem Soc 108 2588 1986]. 

In the case of mechanism (6) there are materials available which completely prevent chain growth by reacting preferentially with free radicals formed to produce a stable product. These materials are known as inhibitors and include quinone, hydroquinone and tertiary butylcatechol. These materials are of particular value in preventing the premature polymerisation of monomer whilst in storage, or even during manufacture. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials May attack some forms of plastics Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent,- Polymerization Hazardous polymerization unlikely to occur except when in contact with alkali metals or metallo-organic compounds Inhibitor of Polymerization 10 -20 ppm tert-butylcatechol. 

Phenolic inhibitors such as hydroquinone (35), monomethylhydroquinone p-metboxyphenol) (36) and 3,5-di-r-butylcatechol (37) are added to many commercial monomers to prevent polymerization during transport and storage. 

Reagent-grade benzyl alcohol was purified by distillation, b.p. 205°. 4-terf-Butylcatechol purchased from Aldrich Chemical Company was sublimed at 50° (0.1 mm.) and recrystallized from hexane. 

Benzyl alcohol (8) Benzenemethanol (9) (100-51-6) 4-tert-Butylcatechol Pyrocatechol, 4-tert-butyl- (8) 1,2-... 

Mechanisms depending on carbanionic propagating centers for these polymerizations are indicated by various pieces of evidence (1) the nature of the catalysts which are effective, (2) the intense colors that often develop during polymerization, (3) the prompt cessation of sodium-catalyzed polymerization upon the introduction of carbon dioxide and the failure of -butylcatechol to cause inhibition, (4) the conversion of triphenylmethane to triphenylmethylsodium in the zone of polymerization of isoprene under the influence of metallic sodium, (5) the structures of the diene polymers obtained (see Chap. VI), which differ. both from the radical and the cationic polymers, and (6)... 

A temperature of 30-40 C and a moderate pressure are enough to cause a violent polymerisation, which can increase the pressure in the reactor to 1000 -1200 bar. In storage, a low polymerisation can also be dangerous for a different reason. In this case, polymer precipitates in the form of flakes causing the volume to rise, which can eventually cause the storage tanks to detonate. Butadiene can only be stored if it contains a poiymerisation inhibitor, which also plays the role of an oxidation inhibitor. Tert-butylcatechol concentrated at 0.2% is perfect for this use, but rust and water can damage the inhibitor. 

The development of catalysts for the efficient oxidation of catechol and its derivatives in water is topic of ongoing work in this laboratory. Towards this end, polyethylene glycol side-chains were incorporated in a pentadentate salen ligand to enhance the water solubility of the complexes derived thereof. A dinuclear copper(II) complex is found to catalyze the oxidation of 3,5-di-tert.-butylcatechol into 3,5-di-tert-butyl-o-benzoquinone more than twice as fast in aqueous organic solution as in purely organic solvents (ly,at/knon= 140,000). Preliminary data are discussed. 

In our ongoing efforts to develop oxidation catalysts that are functional in water as environmentally berrign solvent, we synthesized a water-soluble pentadentate salen ligand with polyethylene glycol side chairts (8). After coordination of copper(II) ions to the salen ligand, a dinuclear copper(II) complex is obtained that is soluble in water, methanol and mixtures of both solvents. The aerobic oxidation of 3,5-di-tert.-butylcatechol (DTBC) into 3,5-di-terr.-butylqitinone (DTBQ) was used as a model reaction to determine the catalytically active species and initial data on its catalytic activity in 80% methanol. 

Catalytic oxidation of 3,5-di-tert.-butylcatechol. The catalytic oxidation of 3,5-di-teri.-butylcatechol, DTBC (8), to 3,5-di-teri.-butylquinone, DTBQ (9), was chosen as a model reaction to test our hypothesis and establish the catalytic abilities of 1 and 7 in organic and aqueous organic solution (eq. 4). 

A dinuclear salen complex was investigated as catalyst for the aerobic oxidation of 3,5-di-ferf.-butylcatechol into 3,5-di-teri.-butylquinone in organic and aqueous organic solution. The actual catalyst composition varies in both solvent systems. Formation of a mononuclear species competes with formation of a dinuclear copper(ll) catalyst. The aerobic oxidation of 8 into 9 is 140,000-fold accelerated over background in aqueous methanol, and is about twice as fast as the same reaction in pure methanol. 

TLC-Raman laser microscopy (X = 514 nm) in conjunction with other techniques (IR microscopy, XRF and HPLC-DAD-ESI-MS) has been used in the analysis of a yellow impurity in styrene attributed to reaction of the polymerisation inhibitor r-butylcatechol (TBC) and ammonia (from a washing step) [795]. Although TLC-FT-Raman did not allow full structural characterisation, several structural elements were identified. Exact mass measurement indicated a C20H25O3N compound which was further structurally characterised by 1H and 13C NMR. 

The preparation and characterization of five co-ordinate [(triphos)Ir(cat)]Z, H2cat = 9,10-phen-anthrenecatechol, 1,2-naphthalenecatecol, 3,5-di-tert-butylcatechol, 4-methylcatechol, 4-carboxy-catechol Et ester, tetrachlorocatechol, Z=BPh4, PF6, have been reported.244 All compounds... 

Polymerization is inhibited or retarded by the presence of certain substances, e.g., p-benzoquinone, 4-t-butylcatechol, 1,3,5-trinitrobenzene, and oxygen. These substances react with radicals to yield species which are no longer capable of chain propagation. The deliberate addition of such substances is useful for stabilizing monomers during transportation and storage. 

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