No abstract

Starch applications in the plastics industry have been investigated intensively for many years. Unfortunately, native starch is unsuitable for most applications in polymers, because of its hydrophilic and brittle character. Modification of native starch can be a solution of this problem.In our research programme we developed an environmentally friendly process for the preparation of starch derivatives with long hydrophobic side chains based on natural products derived from vegetable fats and oils on the one hand and amylomaize starch on the other hand. In this process modification is carried out by the addition of longchain 1,2-epoxyalkanes (chain lengths varying between 6-18 C atoms) to starch in an alkaline aqueous medium. Reaction yields and molar degrees of substitution depended on chain length, reaction time, temperature and catalyst concentration. Under optimised reaction conditions molar degrees of substitution of hydroxyalkyl starch ethers for theoretical molar substitution (MS) = 3.0 decreased from MS=1.8 (C 6 starch ether) to MS=0.2 (C 18 starch ether), respectively. Hydrophobic properties of starch products were measured in order to reveal structural effects obtained at different reaction conditions. Water solubility and water absorption properties of hydroxyalkyl starch ethers decreased with increasing chain length and number of hydroxyalkyl substituents. Thermal and thermoplastic properties of starch ethers were investigated in order to determine their potential use as biodegradable polymers in the plastics industry. As expected, thermoplasticity of starch ethers increased with increasing MS and increasing chain length of the hydroxyalkyl side groups. Scheme 1. Reaction scheme for the preparation of hydroxyalkyl starch ether (MS = 1).

Abstract-

Trinuclear Dithiadiaza[3.3.2]cyclophan‐enes The following five trinuclear dithiadiazacyclophanes have been prepared by means of the rigid‐group principle with a succinyl and dimethylmalonyl N,N′‐protecting group, respectively, and the high‐dilution technique: 2,11‐dithia‐19,20‐diaza[3.3.2]‐(1,4)(1,4)(1,4)cyclophan‐19‐ene (12), 2, 11‐dithia‐19,20‐diaza[3.3.2]‐(1,3)( 1,4)( 1,4)cyclophan‐19‐ene (13), 2,l l‐dithia‐19,20‐diaza[3.3.2]‐(1,4)(1,3)(1,3)cyclophan‐19‐ene (14), 2,11‐dithia‐19,20‐diaza[3.3.2]‐(1,3)(1,3)(1,3)cyclophan‐19‐ene (15), and 4,6‐dimethyl‐2,9‐dithia‐17,18‐diaza[2.2.2]( 1,3)(1,3)(1,3)cyclophan‐17‐ene (16). These cyclophanes contain an azobenzene moiety bridged in the case of 12 and 13 in the para‐positions by a benzene ring and two short links which forces 12 and 13 into a cis‐azo configuration. 14 – 16 are bridged in the meta‐positions of the azobenzene and can adopt a cis‐ and a trans‐azo configuration, respectively. 14 ‐ 16 are photoisomerized into the cis form by irradiation with γ = 369 nm. The isomerization back into the trans form occurs slowly thermally or rapidly by irradiation with λ = 443 nm.

4,4-Dimethyl-l,2-bis(4-methylphenyl)-3,5-pyr~lidindion (4), 12-Bis(4-methylphenyl)perhydro-3,6-pyridazindion (5) und 1 ,2-Bis(4-methylphenyl)perhydro-3,7-diazepindion (6) wurden durch Kondensation von p-Hydrazotoluol mit den entsprechenden Dicarbonsiiuredichloriden dargestellt und durch Photobromierung in die Brommethylderivate 7 -9 GbergeTUhrt. Die Eignung von 7 -9 als Vorstufen fiir die Synthese von 2-Thia-IO,ll-diaza[3.2]paracyclophan-10-en (2) und 2,5-Dithia-l3,14-diaza[6.2]paracyclophan-13-en (3) wurde gepriift. Die Darstellung von 2 gelang unabhlngig von der Ringgriik und Konformation von 7-9 nicht.3 wird dagegen in allen Fallen glatt gebildet, wobei sich der Dimethylmalonylrest wegen der guten Zugiinglichkeit, Stabilitiit und leichten Abspaltbarkeit im alkalischen Milieu besonders be- gelang bisher nur die Synthese des N,N-Phthaloylderivats des Paraisomeren 2 durch Ausnutzen eines ,,Caesiumeffekts" ' ) bei der Cyclisierung nach Schema 1 ' ). bis(4-methylphenyl)perhydro-3,7-diazepin (6) have been prepared by condensation of p-hydrazotoluene with the appropriate dicarbonyl dichlorides and then converted into the corresponding bis(bromomethy1) derivatives 7 -9 by photobromination. 7 -9 have been tested as starting compounds for the synthesis of 2-thia-lO,ll-diaza[3.2]paracyclophan-lO-ene (2) and 2,5dithia-13,14-diaza[6.2]paracyclophan-l3-ene (3). In no case 2 has been obtained, independent of the ring size and conformation of 7-9. However, 3 was readily formed from all precursors; the dimethylmalonyl moiety proved to be convenient as a protecting group because of its ease of preparation, its stability, and its facile cleavage by alkali.