(Distinctive Doe)
07-11-02 10:19
No 331210
      Selenium Dioxide Synthesis
(Rated as: excellent)

This one's for you wink

Preparation of selenium dioxide.   
Meyer, Julius.   
Ber. (1922),  55B  2082-4.
The following process, which depends on the fact that oxidation of Se by O2 is catalyzed by NO, is recommended as giving a product of high purity with great economy of time.  60-75 g. com. Se in a large porcelain boat is placed in the forepart of a hard glass tube 4-5 cm. wide and 50-70 cm. long.  The forepart of the boat is heated until the Se begins to fuse and a very rapid stream of O2 passed through fuming HNO3 into the tube.  A long, luminous, blue flame soon appears over the Se and white SeO2 distils off.  With too slow a current of O2 it is, contaminated by black Se.  To prevent stoppage of the tube the crust of SeO2 is from time to time, sublimed further along the tube by heating with a second burner.  Combustion of 60-70 g.  Se requires about 1.25 hrs.  One resublimation in pure O2 serves to remove oxides of N retained by the SeO2.  To prevent loss of material a 2 l. double tubulated glass bulb is placed over the further end of the sublimation tube.  Contrary to Kuzma and Krehlik (C.A. 5, 1375, 1881) pure SeO2 can be prepd. in glass.

The color of selenium dioxide.
Meyer, Julius; Languer, Margot.   
Ber.  (1927),  60B  285.
SeO2 crystals and aq. and alk. solns. are colorless.  The vapor is yellowish green.  Melting the crystals by heating in a closed tube to 350 gave an orange yellow liquid and yellowish vapor.  The color is not due to Se, since dissocn. did not occur.  Solns. of SeO2 in concd. sulfuric or selenic acids are colored, especially when heated. 

Selenium dioxide
Patent DE279005
Se is oxidized by hot air to pure selenium dioxide, but the Se does not burn quantitatively, subliming in part with the formed SeO2 in the receiver.  The Se is completely oxidized if the heavy Se vapor is most thoroughly mixed with the air.  The Se vapor is conducted through an indifferent heated layer, with excess air, to effect a homogeneous mixt.  Air is conducted over molten Se in such manner that the resulting mixt. of Se vapor and air contains an amt. of air in great excess over that required for the oxidation of the Se.  The gases are then conducted through a more highly heated layer of an indifferent porous material, such as sea sand, asbestos, fire brick, or mixts. of these bodies, whereby the Se vapor is burned quant. to SeO2, which seps. in the form of snow-white needles.

Pure Selenium dioxide
Patent GB603133
Molten Se is vaporized by a stream of O-contg. gas and the resultant mixt. passed over a catalyst (I) at 700-800F.  The product gases are cooled and solid finely divided cryst. SeO2 of extreme purity is recovered.  I is either Cu or Cr or Mn oxide on a ceramic carrier with or without (in the case of Cr and Mn) addnl. alkali metal oxides, e.g., K2O.  I is conveniently prepd. by impregnating II with an aq. soln. of Cu(NO3)2, K2Cr2O2, or KMnO4, and then drying and calcining.

Selenium dioxide
Patent SU1142443
Se is oxidized with HNO3, the resultant soln. boiled down and SeO2 sepd. and purified.  The content of basic substance in the product is increased and the process simplified by carrying out the purifn. of SeO2 by dissolving it to satn. in 70-95% H2SO4 and then sepg. the product from the soln. by increasing the H2SO4 concn. to 99-100%.

Barium selenite.
Patent RO77663
Pure anhyd. BaSeO3, suitable for use in the glass industry, is prepd. by treating aq. solns. of Na2SeO3 with a 10% excess of aq. BaCl2 at 50-60, followed by sepn. of the pptd. product from the aq. mixt. contg. most of the impurities, esp. the resulting NaCl.  Thus, Se (98% pure) was treated with concd. HNO3 and the reaction mixt. was evapd. to dryness to give SeO2.  Then the SeO2 was dissolved in H2O and the pH adjusted with aq. NaOH to 7.6-8.2.  An aq. soln. of BaCl2 was added in 10% excess.  The resulting ppt. was sepd. by filtration and washed and dried at 80-90 to yield an anhyd. totally BaSeO4-free product.

High purity selenium dioxide
Soshnikova, L. A.; Rozhavskii, G. S.; Paikin, V. A.; Buntovnikov, A. S.; Andreeva, V. A.
U.S.S.R.  (1969),
SU223790  19690203  Patent written in Russian. 
High purity SeO2 is prepd. by oxidizing elemental Se with O or O-contg. gas during heating, with subsequent condensation of the SeO2.  Before condensation, the SeO2 is filtered through a dense filter, such as glass wool, at 400-500.  Condensation takes place at 140-317.

Purification of selenium dioxide
Patent DE2263407
SeO2 is purified by passing it with N carrier gas through a heated sepg. column, filled with alkali-contg. ceramic spheres as adsorbent for As2O3, at inlet and outlet temps. 450 and 320, resp., and condensation in a receiver at <316.  This procedure was applied to the purifn. of Se by oxidn., distn., and redn. 

Reclamation of high purity selenium, tellurium, and arsenic from scrap alloys.
Patent US4411698

Manufacture of selenium additives as trace feed elements.
Wira, kTomasz; Gorecki, Henryk; Dobrzanski, Zbigniew.    Nawozow Mineralnych Politechniki Wroclawskiej  (1996),  45(Chemia dla Rolnictwa: Nauka, Przemysl, Ekologia, Marketing),  223-230.
ISSN:0084-2893.  Journal in Polish.
Selenium is an important microelement in animal feed.  Selenium deficiency causes several diseases which are destructive for farming.  In Poland there is a low concn. of selenium in soils and whatsoever in feeds.  Available selenium prepns. are impure (for example arsenium).  It is necessary to elaborate on a chem.-phys. basis for the process and simulation of selenium compd. prodn. on a model scale and then presenting a conception of these as additives for feeds.  This paper shows experimentation, current technol., a simple scheme of sodium selenin and selenate prepn. and the possibility of using sublimation of selenium dioxide as an effective method of impurity redn. for using these compds. in the feed industry. 

Recovery of selenium in sludge.
Patent JP54054918
Sludge contg. Se is heated at 450-550 and then at 650-750 in an air stream.  Thus, sludge contg. <1 g Se was heated at 550 and then at 750 for 3 min each in an air stream 0.5 L/min to recover 93.8% of the Se as SeO2, as compared with 87.7% when heated at 700 only. 

Those who give up essential liberties for temporary safety deserve neither liberty nor safety
(Bee without a Title)
07-11-02 22:14
No 331374
      has anybee tracked that demethylation reference ...  Bookmark   

has anybee tracked that demethylation reference yet? i curious about the yeild and byproducts abnd whether or not it has wider application that the proceedure Neil Bohrs posted.

If somebee were to share it with me i'd be indebtedsmile
(Distinctive Doe)
07-11-02 22:42
No 331384
      what?  Bookmark   

What demethylation reference?  Post in the wrong thread?
I am sure I can get it, if ya tell me what it is.

Those who give up essential liberties for temporary safety deserve neither liberty nor safety
(Bee without a Title)
07-12-02 03:27
No 331489
      ../rhodium/chemistry/asarone.seo2.  Bookmark   

../rhodium/chemistry /asarone.seo2.html

i just assumed that was what you had in mind when you posted the SeO2 synth, i've had a difficult time thinking of much else since i saw it. So i wanted to look at this as it might rteference some other usful stuff:

[1] Rao & Subramaniam, Journal of the Chemical Society 1338 (1937)

any luck with the Nature article?
(Distinctive Doe)
07-12-02 06:17
No 331567
      ok  Bookmark   

I'll get them both tomorrow.
I Promise wink

I added some refs to the first post if anyone missed that

Those who give up essential liberties for temporary safety deserve neither liberty nor safety
(Hive Bee)
07-12-02 21:40
No 331798
      professional pessimist views  Bookmark   

well, that asarone demetoxylation CAN NOT work. Reasons:

1. scientist names are typically Indian. Nothing racistic, but in certain cases (particulary when things described are too good or unexpected) it's just red alert sign. (more recent example - flopped alcohol to nitro article was Indian too)

2. look at article's year - 1937. My god, they had none of modern spectroscopic and other analytical methods at that time, it was not possible to prove compound's structures without very laborious and time consuming derivatisation and degradation methods (seems that in this case it was done quite superfically)

3. There's just no meaningful way, how this conversion might proceed. (SeO2 is oxidiser, but supposed reaction formally is reduction!)
(Bee without a Title)
07-12-02 21:50
No 331801
      lots laughed at the Zn/HCl reduction too, and ...  Bookmark   

lots laughed at the Zn/HCl reduction too, and i've seen countless posts over the years exclaiming at its failures, YET! it works like a charm.

i would like to read it all the same, if for no other reason than to see what similar works it might reference. As far as the researcher being Indian, well thats where the stuff grows, i'd be more skeptical of eskimo researchers making those claims.
(Bee without a Title)
07-12-02 23:26
No 331828
      There's just no meaningful way, how this ...  Bookmark   

There's just no meaningful way, how this conversion might proceed. the following patents seem to suggest selenium is capable of complexing with carbonyls

United States Patent 5,994,151
United States Patent 4,166,820
United States Patent 6,040,197

wouldn't that indicate utilty beyond use a simple oxidant?
(Hive Addict)
07-13-02 22:50
No 332156
      Merck name reaction involving selenium dioxide  Bookmark   

Riley oxidation.  reaction 340 see merck.
Oxidation of active methylene groups to carbonyl groups.