Tellurous acid anhydride

Formula Te02 MW 159.60 Synonym tellurous acid anhydride... 

Tellurous acid anhydride. See Tellurium oxide TEM. See Triethylenemelamine TEMED. SeeN,N,N, N -Tetramethylethylenediamine Temephos CAS 3383-96-8... 

Te (tellurium, brown black, amorphous), Te02 (tellurous anhydride, white), Te02 hydr. (tellurous acid, H2Te03 or Te02-H20, white, amorphous), TeOs hydr. (orthotelluric acid, H6Te06 or Te03 3H20, colorless, cubic or monoclinic). 

Tellurium Dioxide as an Acid Anhydride.—When tellurium tetrachloride is treated with water, or when an aqueous solution of a tellurium salt is decomposed by an aqueous alkaline solution, a bulky, colourless precipitate is obtained which is sufficiently soluble in water to impart an acid reaction to the solution and which is more readily soluble than tellurium dioxide in acids or alkalis. A similar precipitate is obtained on acidifying a cold aqueous solution of potassium tellurite with a slight excess of nitric acid. This product is a tellurous acid, possibly H2TeOs, but it is very unstable and spontaneously dehydrates, slowly at the ordinary temperature and rapidly at 40° C. with formation of dioxide.1... 

Among activated forms of amino acids, mixed anhydrides with inorganic phosphate or phosphate esters require a special discussion because they are universally involved in peptide biosynthesis through the ribosomal and non-ribosomal pathways. These mixed anhydrides have stimulated studies in prebiotic chemistry very early in the history of this field. Amino acyl adenylates 18c have been shown to polymerize in solution [159,160] and in the presence of clays [139]. However, their participation as major activated amino acid species to the prebiotic formation of peptides from amino acids is unlikely for at least two reasons. Firstly, amino acid adenylates that have a significant lifetime in aqueous solution become very unstable as soon as either CO2 or bicarbonate is present at millimolar concentration [137]. Lacey and coworkers [161] were therefore conduced to consider that CO2 was absent in the primitive atmosphere for aminoacyl adenylate to have a sufficient lifetime and then to allow for the emergence of the modern process of amino acid activation and of the translation apparatus. But this proposition is unlikely, as shown by the analysis of geological records in favor of CO2 contents in the atmosphere higher than present levels [128]. It is also in contradiction with most studies of the evolution of the atmosphere of telluric planets [30,32], Secondly, there is no prebiotic pathway available for adenylate formation and ATP proved to be inefficient in this reaction [162]. 

---