Diethyl zinc, paper

Kragl and Dreisbach (1996) have carried out the enantioselective addition of diethyl zinc to benzaldehyde in a continuous asymmetric membrane reactor using a homogeneous soluble catalyst, described in their paper. Here a,a-diphenyl-L-proline was used as a chiral ligand, coupled to a copolymer made from 2-hydroxy ethyl methacrylate and octadecyl methacrylate, which had a sufficiently high molecular weight to allow separation by ultra-filtration (U/F). The solvent-stable polyaramide U/F Hoechst Nadir UF PA20 retained more than 99.8% of the catalyst. The ee was 80 %, compared to 98 % for a noncoupled catalyst. 

DEZ [Diethyl zinc] A process for preserving books and documents by treatment with diethyl zinc vapor, which neutralizes ary residual acidity from the papermaking process. The articles are placed in a low-pressure chamber and suffused by diethyl zinc vapor. This vapor reacts with the moisture in the paper to yield zinc oxide, which neutralizes the acid. The process was developed by Texas Alkyls (a joint company of Akzo and Hercules) and the U S. Library of Congress. A pilot plant was set up in 1988, capable of treating batches of 300 books, and plans to build two larger plants were announced in 1989. 

Sulfite paper has a relatively short life span, since residual acid will continue to hydrolyze the cellulose and cause embrittlement. Further sources of acid include aluminum sulfate (which is added together with resin to suppress bleeding or feathering of ink into the paper) and S02 and NO from the atmosphere. Much of the world s library collections and archives will soon be lost as the paper crumbles. Various deacidification treatments (e.g., with ammonia, morpholine, cyclohexylamine carbamate, or diethyl-zinc) have been proposed and tried, but at best they can only halt the process of embrittlement and cannot reverse it.14 With the move to kraft pulping, alkaline peroxide bleaching, and increasing use of precipitated calcium carbonate as a filler, the high quality papers produced today are intrinsically acid free and should also resist subsequent acidification by S02-polluted air fairly well. 

The reaction of diethyl zinc with water produces zinc oxide, and then zinc carbonate, as the alkaline reserve. These chemicals have antiseptic properties which may also prevent the growth of mold in paper. They may also improve the brightness of treated papers. However, it is also known that zine oxide is a photosensitizer (56) which may trigger photo-oxidation of treated papers to initiate a chemical chain reaction that will lead eventually to the formation of acidic products (57). Moreover, the interaction of zinc oxide and zinc carbonate with copper, iron and cobalt present in the paper and their subsequent effects on paper stability have not been studied. 

This paper describes the theory which permits us to characterize adequately the stereosequence length in stereoregular polymers from the equilibrium percent crystallinity at room temperature and from the melting points of the polymers. Results based on this theory are given on the characterization of the isotactic stereosequence length in the crystalline fractions of polypropylene oxide polymers made from the following catalyst systems (a) ferric chloride (17, 19) (b) diethyl zinc-water (10) (c) diethyl zinc-water-isopropylamine (d) diethyl zinc-water-cyclohexylamine (14). 

Inhibition of Light Sensitivity of Papers Treated with Diethyl Zinc... 

A series of papers containing varying amounts of zinc oxide was selected from among those that had been treated with diethyl zinc in the development of the treatment process. The properties of these papers before and after treatment are shown in Table I. All papers were conditioned by TAPPI Method T-402 before testing. Samples of the treated papers and the untreated controls were exposed for 88 h to the light of... 

The six papers selected for the investigation of increased light sensitivity with zinc oxide covered the range of zinc oxide contents usually found in the diethyl zinc treatments 2.2% —5.1% zinc oxide. Most of the... 

The conversion to carbonate was tried with a 400-book treatment run in which the excess diethyl zinc was destroyed with alcohol after partially backfilling the chamber with carbon dioxide. After adding water to hydrolyze the zinc cellulosate compound, the backfilling with carbon dioxide was continued to nearly atmospheric pressure to force the damp carbon dioxide into the books. At the same time, the atmosphere in the chamber was circulated with a fan for 24 h to insure good contact. After such treatment, paper samples from the books showed effervescence when immersed in dilute acid, indicating the presence of carbonate. Samples of paper from books previously treated with diethyl zinc (where the carbon dioxide was not used) showed no such effervescence. 

With this demonstration that zinc carbonate does not catalyze the photodegradation of paper in the presence of UV light and high humidity, we feel that the diethyl zinc process, as modified by the final carbon dioxide exposure, is now commercially feasible. 

In discussing this problem over lunch, a colleague suggests the compound diethyl zinc, (C2H5)2Zn, which is quite volatile (boiling point = 117°C) and which reacts with water (moisture is present in paper) as follows ... 

After much testing, chemists developed a compound that stabilizes paper diethyl-zinc [Zn(C2H5)2]. Diethylzinc is volatile so it can be sprayed onto books. It reacts with water to form zinc oxide (ZnO) and gaseous ethane (C2Hg). (a) Write an equation for this reaction, (b) ZnO is an amphoteric oxide. What is its reaction with H+ ions ... 

Diethyl zinc is used in organic synthesis. It is also used in preservation of archival papers. 

Thus the ZnO is a nonvolatile base that can be placed in the paper by a gaseous substance. This process seems very promising. However, the major disadvantage of this process (there are always disadvantages) is that diethyl zinc is very flammable and great care must be exercised in its use. This leads to another question Is the treatment effective enough to be worth the risks involved Only through more experiments can this question be answered. 

Benzisothiazolin-3-one Benzoyl peroxide preservative, archival papers Diethyl zinc... 

Diethyl zinc (1952) n. C4H10Z11. A volatile pyrophoric liquid organometallic compound used to catalyze polymerization reactions and to deacidify paper. 

A number of recent papers describe the use of high resolution NMR spectroscopy in identifying stereosequence distribution in polypropylene oxide (9-11,17-20). Using or-deuterated polypropylene oxide and 220 HMz NMR, Oguni et al (19) have shown that the shift in methylene absorbtion can be used to identify the structures assigned to tail-to-tail linkages and to isotactic and syndiotactic triads. They showed that the crystalline fraction of polymer prepared with a diethyl-zinc-water catalyst system did not contain a measurable amount of tail-to-tail linkages. 

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