Co-sublimation

CARBON DIOXIDE. (CAS 124-38-91. CO., formula weight 44.01. colorless, odorless, nonloxic gas at standard conditions. High concentrations of the gas do cause stupefaction and suffocation because of the displacement of ample oxygen for breathing. Density 1.9769 g/l (O C. 760 ton). sp gr 1.53 tair — 1.00). mp -56.6"C (5.2 atmospheresl. solid CO sublimes at -79°C (760 torr). critical pressure 73 atmospheres, critical temperalure 3I C. Carbon dioxide is soluble in HiO (approximately I volume CO. in I volume H.O at 15 C. 760 tom. soluble in alcohol, and is rapidly absorbed by most alkaline solutions. The solubility of CO in H 0 for various pressures and temperatures is given in Table I. 

In an interesting twist on the solvent free reaction, Petrukhina and coworkers co-sublimed a volatile metal complex, [Rh2(CF3C02)4], and arene molecules including paracyclophanes to yield organometallic coordination polymers. Moderate yields of crystalline products were obtained (35-70%),... 

The bromo analogue is made from K2lrBr6. The chloro derivative is also made by (1) adsorbing IrCls xHjO on silica gel, (2) preheating to 120°C (to dryness), and (3) heating to 150°C with first a stream of CI2, then CO. Sublimation at 160-180 C in CO purifies the material. 

Yellow prisms from EtOH. DLp. 62 . Sol. hot EtOH, CHCL, Me,CO. Sublimes. Volatile in steam. D 2 356. Ale. NHg—>>5-bromo-o-nitroaniline. 

If elemental arsenic is present, it will co-sublime with the NH4CI and give a black mirror. In this case, it is necessary to heat the sublimed material in 1 Af hydrochloric acid and filter. The filtrate is then tested for antimony as described on page 106. 

PPha, pyridine) organic groups (olefines, aromatic derivatives) and also form other derivatives, e.g. halides, hydrides, sulphides, metal cluster compounds Compounds containing clusters of metal atoms linked together by covalent (or co-ordinate) bands, metaldehyde, (C2H40) ( = 4 or 6). A solid crystalline substance, sublimes without melting at I12 1I5" C stable when pure it is readily formed when elhanal is left in the presence of a catalyst at low temperatures, but has unpredictable stability and will revert to the monomer, ft is used for slug control and as a fuel. 

Crystallizes from water in large colourless prisms containing 2H2O. It is poisonous, causing paralysis of the nervous system m.p. 101 C (hydrate), 189°C (anhydrous), sublimes 157°C. It occurs as the free acid in beet leaves, and as potassium hydrogen oxalate in wood sorrel and rhubarb. Commercially, oxalic acid is made from sodium methanoate. This is obtained from anhydrous NaOH with CO at 150-200°C and 7-10 atm. At lower pressure sodium oxalate formed from the sodium salt the acid is readily liberated by sulphuric acid. Oxalic acid is also obtained as a by-product in the manufacture of citric acid and by the oxidation of carbohydrates with nitric acid in presence of V2O5. 

The O oxidation state is known in vanadium hexacarbonyl. V(CO)(,. a blue-green, sublimable solid. In the molecule VfCO), if each CO molecule is assumed to donate two electrons to the vanadium atom, the latter is still one electron short of the next noble gas configuration (krypton) the compound is therefore paramagnetic, and is easily reduced to form [VfCO, )]. giving it the... 

CsH5)3Ti [39333-58-9] Ti(III) Cp3 green sublimes at 125 extremely air-sensitive gives (C3H3)2Ti(CO)2 with CO under... 

The approximate calculation of the surface energies of metals as a function of crystal structure described earlier uses the enthalpy of sublimation, s, and the co-ordination number to calculate the energy as a function of the atomic concentration on the surface. The atomic areas of the principal configurations are as follows ... 

Has been purified by co-distillation with ethylene glycol (boils at 197.5°), from which it can be recovered by additn of water, followed by crysm from 95% EtOH, benzene, toluene, a mixture of benzene/xylene (4 1), or EtjO. It has also been chromatographed on alumina with pet ether in a dark room (to avoid photo-oxidation of adsorbed anthracene to anthraquinone). Other purification methods include sublimation in a N2 atmosphere (in some cases after refluxing with sodium), and recrystd from toluene [Gorman et al. J Am Chem Soc 107 4404 1985]. 

A mixture of ethyl 1//-azepine-l-carboxylate (24, R = Et 2.74 g, 17.3 mmol) and pentacarbonyliron(O) (4.16 g, 22 mmol) inTHF (25 mL) was irradiated with UV light for 30 h, during which time CO (g)(710mL) was evolved. (Caution reaction must be carried out in an efficient fume hood). The solution was reduced in volume and the residue chromatographed (neutral alumina, hexane). After removal of the solvent the product was purified by sublimation under high vacuum at 60 C yield 4.04g (77%) mp 87°C. The tricarbonyliron(O) complex of ethyl 2,4,7-trimethyl-1//-azepine-1-carboxylate (11.6% mp 54 C) was prepared similarly. 

Ethyl 1//-l,2-diazepine-l-carboxylate (0.50g, 3.1 mmol) in benzene (100 mL) was treated with Fe2(CO)9 (1.50 g, 4.1 mmol) and the mixture was vigorously agitated at 20 C under N2. The mixture was filtered, the filtrate was evaporated and the residue was chromatographed (silica gel, EtOAc/cyclohexane 2 3) to give the product, which was sublimed at 60°C/0.04Torr yellow crystals mp 115 C. (The yield was not reported.)... 

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