Materijali za novo tisućljeće - anorganski, polu-anorganski i organsko-anorganski hibridni polimer

The properties of mineralogical and covalent inorganic polymers are brieffy described in the introductory part. Glass is an important polymer made up of rings and chains of silicate units which contain negatively charged oxygen atoms neutralized by positive metal ions. Glass and few other mineralogical types of inorganic polymers, like aluminum oxyde, could be fabricated into fibers and used as insulating materials, and as reinforcing fibers in composite materials. Most rocks, bricks, concrete and ceramics belong to mineralogical polymers which are of great importance as construction materials, but their application is often limited because they are not flexible, elastomeric and resistant to impact. The most important covalent polymers are poly(organosiloxanes) and poly(organophosphazenes). Poly (organosiloxanes) contain chains of silicone-oxygen atoms with two methyl groups attached to silicon atoms. Silicone polymers have low glass transition temperature of -130 °C. Temperature of elasticity of silicone rubber is from -30 °C to 250 °C. They strongly repel water and are used as corrosion inhibitors of metals. An important field of application of silicones is in medicine and in preparation of medical devices. In continuation, there are briefly described the properties and application of poly(phosphazenes) and poly(sulfur nitride). After that, several examples of organic-inorganic hybrid polymers are listed, illustrating the variety of existing and possible new commercial applications of these new materials. The following applications of hybrid polymers are described: silane block copolymers for contact lenses, acrylate tin copolymers for marine antifoulant coatings, scratch resistant automotive coatinas and preparation of microporous silica.U referatu je naglašeno da iako su mnogi anorganski sintetski polimeri otkriveni prije organskih sintetskih polimera, anorganski polimeri značajno zaostaju u razvoju u usporedbi s organskiin polimerima koji se proizvode na osnovi petrokemijskih sirovina. Međutim i pored prednosti koje imaju organski sintetski polimeri u usporedbi s anorganskim polimerima, oni se ne mogu primjeniti u mnogim područjima visokih tehnologijja u kojima se zahtjevaju materijali otporni na visoke temperature uz uvjete korodirajuće atmosfere. Očekuje se da će mnogi problemi povezani s primjenom organskih polimera biti savladani razvojem nove generacije anorganskih polimera. Od posebnog su značaja polu-anorganski polimeri koji sadrže anorganske elemente u glavnom lancu, a organske skupine kao bočne grane, te organsko-anorganski hibridni kopolimeri, koji su se počeli razvijati u zadnje vrijeme. Anorganski polimeri klasificiraju se na razne načine, a najčešće kao mineraloški i kovalentni anorganski polimeri. Staklo pretstavlja mineraloški tip anorganskih polimera u kojima su postrane skupine negativnih kisikovih atoma neutralizirane pozitivnim nabojima metalnih iona natrija, magnezija ili kalcija. Od kovalentnih anorganskih polimera značajni su poli(organosiloksani) ili silikoni, poli(organofosfazeni) i poli(sumpor nitridi). Molekulska masa silikona iznosi 2x106, a Tg -130 °C uz područje elastičnosti od -30 °C do 250 °C. Silikonski polimeri mogu se proizvoditi jednostavnim tehnološkim postupcima iz jeftinih lagano dostupnih sirovina. Silikoni se koriste za izradu predmeta od keramike, stakla, gume, građevinskog materijala, te u medicini. Značajna je primjena silikona za zaštitu metala od korozije. Poli(di-triffuoretoksifosfazen) se lagano oblikuje iz otopine, tali se kod 242 °C, a Tg iznosi -66 °C. Novo područje anorganskih polimera su anorgansko-organski hibridni polimeri koji se upotrebljavaju za proizvodnju kontaktnih leća, za zaštitu površine metala od korozije i mehaničkih oštećenja od grebanja, te za spriječavanje nakupina na ljusku broda u moru

The Absolute Configuration of 3-Carboxypyrrolidine (B-Proline)

( + )-3-Carboxypyrrolidine was synthesized from ( + )-1-benzyl- 4-carboxy-2-pyrrolidone, and its configuration correlated with ( + )-2-methyl-4-phthalimidobutyric acid of known configuration. The configuration of carbon-3 atom of ( + l-B-proline is shovn to be S

The Correlation of Configuration of Optically Active Nor-pseudo-ephedrine and Alanine

D-Nor - pseudo- ephedrine was prepare d from N-phthaloyl-D-alanyl chloride through the intermediate D-a-phthalimido-propiophenone which was reduced with aluminum isopropoxide to the appropriate carbinol. L-Nor- pseudo-ephedrine was prepared in the same way from L-alanine. The configurational correlation between D-nor-pseudo-ephedrine and D-alanine a nd L-nor- pseudo-ephedrine and L-alanine was established. The configurational relation of C(2) atom of chloramphenicol and D-(-)-nor - pseudo - ephedrine was thus established since chloramphenicol was previously synthetized from D-serine

The Correlation of Configuration of Optically Active Nor-pseudo-ephedrine and Alanine

D-Nor - pseudo- ephedrine was prepare d from N-phthaloyl-D-alanyl chloride through the intermediate D-a-phthalimido-propiophenone which was reduced with aluminum isopropoxide to the appropriate carbinol. L-Nor- pseudo-ephedrine was prepared in the same way from L-alanine. The configurational correlation between D-nor-pseudo-ephedrine and D-alanine a nd L-nor- pseudo-ephedrine and L-alanine was established. The configurational relation of C(2) atom of chloramphenicol and D-(-)-nor - pseudo - ephedrine was thus established since chloramphenicol was previously synthetized from D-serine

Synthetic Studies in the Chloramphenicol Series. IV* Synthesis of threo-DL-Chloramphenicol Base from DL-Serine Methyl Ether

A synthesis of threo-DL-chloramphenicol base from a-bromo-B methoxy-propionic acid, an intermediate in the synthesis of DL-serine methyl ether is described. The synthesis is essentially the same as the one previously described for the preparation of threo-DL-chloramphenicol from DL-serine ethyl ether. However, the over-all yield of chloramphenicol base is much higher (6.9%, based on a-bromo-B-methoxy-propionic acid) mainly due to the high yield of a-phthalimido-B-methoxy-propiophenone, which was obtained in a yield of 63.5 %

Synthesis of Some Quaternary Ammonium Salts Derived from Esters of Muconic Acid

Quaternary ammonium salts of di-(B-dimethylammonium ethyl) -muconate (I) and di-(B-dimethylammonium isopropyl)-muconate (II) , were prepared as possible neuromuscular blocking agents

Synthetic Studies in the Chloramphenicol Series. IV* Synthesis of threo-DL-Chloramphenicol Base from DL-Serine Methyl Ether

A synthesis of threo-DL-chloramphenicol base from a-bromo-B methoxy-propionic acid, an intermediate in the synthesis of DL-serine methyl ether is described. The synthesis is essentially the same as the one previously described for the preparation of threo-DL-chloramphenicol from DL-serine ethyl ether. However, the over-all yield of chloramphenicol base is much higher (6.9%, based on a-bromo-B-methoxy-propionic acid) mainly due to the high yield of a-phthalimido-B-methoxy-propiophenone, which was obtained in a yield of 63.5 %

Synthesis of β-Alethine and Analogues

In the past few years many papers have appeared relating to the problem of the synthesis of B-alethine an intermediate in the synthesis of panthetine. A more recent publication on the synthesis of B -alethine and analogues has prompted us to publish our own results on the synthesis of B -alethine and analogues derived from glycine and O-methyl-DL-serine

Synthetic Studies in the Polyene Series. II.Synthesis of 15,15\u27 -Dihydro-B -carotene

The compound mentioned in the title has been prepared by condensation of 3,8-dimethyl-3,8-dihydroxy-decadiyne-(1,9) with two moles of 4-[2\u27,6\u27,6\u27 -trimethyl-cyclohexene-(l \u27) - y l]-2-methy lbuten-( 3)-al-(l), followed by dehydration and partial hydrogenation of acetylenic bonds. Intermedia tes and the fina l product were purified by absorption chromatography, and their structures were proved by spectroscopic and analytical methods

Synthesis of Some Quaternary Ammonium Salts Derived from Esters of Dihydromuconic Acid

Choline esters of dicarboxylic acids, because of their use as short acting neuromuscular blocking agents, have been in the last few years the subject of wide inivestigations. Bovet and collaborators have studied the relationship between the chain length of ailiphatic dicarboxylic acids and the curariform activity. They found that the activity increases if the length of the chain increases from oxalic to succinic acid, but further lengthening of the chain decreases the paralysing activity. They also claimed that the double bond had no significant influence on the curariform activity