Dihydrol

Water molecules are known to associate in pairs in the liquid state, and Werner therefore justified his suggestion that polymerised molecules of dihydrol or II402 probably occur in hydrates of the former type as also in the alums. These latter are represented as co-ordination derivatives of general formula... 

Pokkuluri et al. have recently addressed the question of the directionality of free volume in their studies on the solid state di-Ti-methane rearrangement of methyl 2-benzoyl-l,4-dihydrol,4-ethenonaphthalene-3-carboxylate, 30 [150]. The title compound gives two different sets of products upon solution and solid state irradiation, both resulting from di-Ti-methane process involving 1,3-diradical intermediate (Scheme 14). Strikingly, the solid state products derive via less stable 1,3-diradical intermediates, 31 and 32 whereas the... 

It remains to be noted that, when there is no method available for ascertaining the formula weight or a compound, the simplest formula, based on chemical analysis and the use of symbol weighLs of the contained elements, is used, e g., ferric oxide, FejOj, ferroferric oxide, FejCXt, ferrous oxide, FeO, cupric oxide (black copper oxide), CuO. cuprous oxide (red copper oxide). CujO. The customary formula of water is H2O. which is correct ai temperatures above I00°C—actually, liquid water is mainly dihydrol (HjOh. 

By the reaction of 4-amino-2,3-dihydro-l,5-benzothiazepine (79) with triethyl orthoacetate at 150°C followed by treatment with ammonia at room temperature, an acetamidine intermediate was obtained which, by oxidative cyclization with sodium hypochlorite, was converted to 4,5-dihydrol[ 1,2,4]triazolo[5, -d [ 1,5]benzothiazepine 6,6-dioxide (98) (Scheme 29) (92M1023). 

A mixture of 680 grams of 2-methyl-9-phenyl-2,3-dihydrol-pyridindene hydrobromide, 6,000 cc of water and about 100 grams of Raney-nickel catalyst is hydrogenated at room temperature and at about 1,000 lb pressure for a period of three hours. The catalyst is filtered. The clear filtrate is treated with a solution of 240 grams potassium thiocyanate in 400 cc of water. A heavy solid precipitates from which the supernatant liquid is decanted. 

As shown in Chapter X., water is believed to be associated to a considerable extent to dihydrol (H2Q)2 and, at low temperatures even to trihydrol molecules, (H20 )3. Assuming the strictly monovalent nature of hydrogen, a higher valency than two is required for oxygen. Thus dihydrol may be written H2=0=0=H2, and to tnhydrol a cyclic formula may be given. 

Bose 9 showed that if water-vapour be regarded as an equilibrium mixture of many hydrol molecules with a few dihydrol, thus... 

If x and y are 2 and 3 respectively, clearly n= n, and 50 per cent, of dihydrol is in equilibrium with 50 per cent, of trihydrol. If. however, y > 3, the value for m must fall if x remains constant. Unless, therefore, the numerical values to be assigned to x and y are known, those for n and m cannot be deduced, and vice versa. Further, the system becomes even more complicated if more than two forms of water are present. 

This idea has been further developed by Sutherland,2 who concludes that ordinary water vapour is monohydrol, H20 liquid water is an equilibrium mixture of tnhydrol, (H20)3, and dihydrol, (H20)2 whilst ice consists entirely of trihydrol. The high value found for the latent heat of fusion of ice thus receives explanation, for it is not due merely to the heat absorption consequent upon physical change of solid to liquid it is enhanced by the heat required to effect the simultaneous dissociation or depolymerisation of a large proportion of trihydrol molecules to the dihydrol form, as indicated by the thermal equation which Sutherland writes as ... 

A similar explanation may be offered for the high values observed for the latent heat of steam. Thus, the thermal dissociation of dihydrol molecules is accompanied by an absorption of 189x18x2 calories, or, expressed as an equation ... 

For dihydrol and trihydrol Sutherland calculates the following physical data (p. 304). 

But even if the water at its critical temperature consisted of nearly pure dihydrol, without any trihydrol molecules, it would still be far more highly associated than calculation from Guye s formula would indicate. As shown on p. 300, when the most recent critical data are employed in the calculation, the molecular weight of water at the critical temperature works out at 18-5, and corresponds to almost absolutely pure mbnohydrol. 

Constitution of Water—Dihydrol and Trihydro]— Water a Ternary Mixture. 

According to this picture there is no longer any question of definite stoichiometrically constituted associations as those formerly assumed to be dihydrol and trihydrol. 

Photolysis of the silyl-substituted phosphirene 19 proceeds selectively with cleavage of silicon-silicon bond and ring expansion to furnish the l,2-dihydro-l,2-phophasilete 20 (Equation 21) <1999CEJ1581>. The corresponding l,2-dihydrol,2-phophagermete is prepared analogously. 

Dihydrol urans. /irconocenc-calalwcd kinetic resolution of 122... 

The DDP-4 inhibitors are chemically variable and their metabolic pathways are different. Sitagliptin, (2f )-4-oxo-4[3-(tri-fluoromethyl)-5,6-dihydrol[l,2,4]triazolol[4, 3-a]pyrazin-7(8H)-yl]-l-(2,4,5-trifluorophe-nyl)butan-2-amine, is primarily eliminated unchanged, 80% being excreted in the... 

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