P-hidroksi benzil kolesteril eter sentezi
Başlık çevirisi mevcut değil.
- Tez No: 75262
- Danışmanlar: PROF. DR. NACİYE TALINLI
- Tez Türü: Yüksek Lisans
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Eterler, Sentez, p-hidroksi benzil, Ethers, Synthesis, p-hydroxybenzyl
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimya Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Kömürler, doğal enerji kaynaklanınız arasında yer almaktadırlar. Bu yüzden, daha iyi yararlanabilmek için onların yapılarını incelemek ve bilmek gerekmektedir. Bu doğal enerji kaynağı en iyi verimi yaşlandığı zaman vermektedir. Bilinen kömür kaynaklarının orijini bitkisel ve hayvansal tortullardan oluşmaktadır. Bu iki tortulun oluşturduğu kömürler steroid kaynaklı yapılan içermektedir. Bu çalışmada, steroid yapısı içeren kömür sedimentlerinin yapısını anlayabilmek için kimyasal yapısı bilinen ve model bileşik olarak isimlendirilen reçinelerin sentezi gerçekleştirilmiştir. Model bileşik olarak; p-hidroksibenzilkolesterol eter veya p-hidroksi- benzilkolestanol eter bileşiklerinin sentezlenmesi amaçlanmıştır. Doğal kaynaklardan elde edilen sonuçlara bağlı olarak bu bileşiklerin seçimi yapılmıştır. Model bileşiğin sentezi için Williamson eter sentezi yöntemi kullanılacaktır. Bunun için çıkış bileşiği olarak p-hidroksi benzil klorür düşünülmüştür. Fakat p- hidroksi benzilklorür kolaylıkla kendi kendine polimerizasyona uğradığı için ticari olarak satılmamaktadır. Bu nedenle fenolik yapıdaki -OH grubunun korunma işlemi düşünülmüştür. Koruyucu grup olarak fenolik eterler ve esterler hazırlanmıştır. İlk olarak p- hidroksibenzil klorür yerine, p-metoksibenzil klorürden yola çıkılması amaçlanmıştır. p-metoksibenzil bromür bazik ortamda kolesterol ile reaksiyona girerek p-metoksibenzil kolesteril eter elde edilmiştir. Serbest -OH grubunu açığa çıkarmak için piridin.HCl ile demetilasyon işlemi yapılmıştır.Reaksiyon sonucunda, demetilasyon işleminin selektif olarak gerçekleştirilemediği, benzilik eter bağıranda koptuğu görülmüştür. Sonuç olarak istenilen bileşiğe ulaşılamamıştır. İkinci yöntemde fenolik yapının ester türevi hazırlanmıştır. Bunun nedeni ester hidrolizi koşullanndan benzil eter bağının etkilenmemesidir. Çıkış bileşiği olarak 4- (benziloksi) benzil bromür(klorür) bileşiği sentez edilmiştir. Elde edilen bu bileşiğin kolesterol ile susuz bazik ortamdaki reaksiyonu sonucu amaçlanan 4- (benziloksi)benzilkolesteril eter yerine trans esterleşme sonucu kolesterilbenzoat oluşmuştur. Üçüncü yöntemde ise çıkış bileşiği olarak p-hidroksi benzaldehit seçilmiştir. Bileşiğin THP-eter türevi hazırlanarak aldehit grubu indirgenmiştir. Elde edilen 4- (tetrahidropiran-2-oksi) benzilalkol tosil klorürle reaksiyona sokularak tosil ester elde edilmiştir. Bu bileşiğin kolesterol ile bazik ortamda gerçekleştirilmeye çalışılan kenetleme reaksiyonu başansızlıkla sonuçlanmıştır. Sonuç olarak fenolik yapı içeren moleküle ulaşılamamıştır. Elde edilen anisil kolesteril eterden reçine oluşturulmuştur. Bunun için lmol anisil kolesteril eter, 3mol fenol ve 3mol formaldehit kanştınlarak 3 gün 70°C ve 1 gün 140°C sıcaklıkta bekletilmiştir. Hazırlanan reçine piroliz ve hidropiroliz işlemleri için İskoçya 'ya gönderilmiştir. vuı
Özet (Çeviri)
SUMMARY P-HYDROXY BENZYL CHOLESTERYL ETHER SYNTHESIZED Oil shale is a compact, laminated rock of sedimentary origin, yielding over 33% of ash and containing organic matter that yields oil when distilled, but not appreciably when extracted with the ordinary solvents for petroleum. The term oil shale is used to denote an organic-rich rock that contains little or no free oil. Shale oil is defined as the oil produced from an oil shale on heating. Three other terms use extensively, hence their definitions are important : Bitumen is defined as the organic material which can be extracted by ordinary organic solvents, such as benzene, toluene, tetrahydroduran (THF), and chloroform, or mixtures of solvents, such as benzene methanol. Kerogen, which comprises the major part of organic material, is not soluble in such solvents. Of course, these are operational definitions and the relative proportions of bitumen and kerogen depend on the choice of solvents and extraction conditions. The third term, kerogen concentrate, refers to the organic concentrate that is produced by benefication or chemical demineralization of an oil shale. This term should refer only to that part of the organic concentrate that is insoluble in organic solvents. Oil shale and coal contains a variety of fossilised plant tissues in different stage of preservation. During the after deposition in sedimentary basins, plant remains undergo a sequence of physical, chemical and biochemical changes, i.e. diagenesis and catagenesis, result in a series of coals of increasing ranks. Extract of fossil fuels frequently contain compounds (biomarkers) whose structures are related to chemical structures in the original flora in ways that provide informatin about the deposition and the diagenesis that formed the fuel. Amongst the biomarkers studies are n- alkanes, in particular the ratio of odd carbon numbered alkanes, branched paraffins, pristane and phytane; cycloalkanes; alkyl-benzenes; substitued naphthalenes; hopanes; tetracyclic terpanes; and steranes. Biological markers are compound detected in the geosphere derived from living organisms whose basic carbon skeleton has survived the processes of diagenesis and thermal maturation. The most commonly studied biomarkers are the cyclic alkenes; the hopanes and the sterans, which are derived from hopanoid and steroid natural product, respectively are ubiquitous components of crude oil, kerogen and coals. As well as providing information about the original biological input the sediments, the disturbution of certain hopane and sterane stereoisomers have been widely used to indicate the thermal stress experienced by fossil organic matter. The biologically synthesized conformation of their precursors are not the most thermally stable and configurational isomerization is observed at certain chiral centers as maturation proceeds. Although these biomarkers are generally only present in small quantities in solvent extracts and pyrolysates, they are readily detectable using IXsingle ion monitoring in gas chromatography-mass spectrometry (GC-MS) without the need for extensive preseparation. To summarize, a series of C27-C35 hopanes is the most commonly observed distribution in ancient sediments but usually the C28 member is missing. The biological 17|3(H) - 210(H) configuration inherited by the alkanes of immature sediments is lost rapidly with increasing maturity forming a mixture of 17a(H), 21p(H) and 17P(H), 21a(H) stereochemistry. Eventually the 17p(H), 21a(H) hopanes also convert to the 17a(H), 2ip(H) form and one selectively depleted relative to the 17a(H), 2ip(H) stereoisomers. The sterol precursors of the tetracyclic steranes are widely distributed in nature and the most commonly encountered sterane those of carbon number C27, C28, and C29, although variable amounts of C21 and C22 isomers with shorter alkyl side chains are also often present. At the later stages of diagenesis, the main stereodial components are usually alkanes and ring“C”mono aromatics. Further, maturation leads to configurational isomerization, aromatization of C-ring monoaromatic steroids to ABC ring tri aromatics and enrichment of the lower molecular weight (MW) components (C20-C22) relative to the higher MW counter parts (C28-C29). OH OH OH OH So, understand the fate of covalently-bound biomarker, model systems are required in which only a single hydrocarbon entity can be incorporated into a macro molecules frame work. In this study, 4-hydroxy benzyl cholesterol, which is going to use model compounds to make comparison between natural fossil fuels and synthetic model compounds to understand organic structure of fossil fuels, was tried to synthetized. The some pyrolysis experiments were be done on the cholesteryl ether resins, these are 1- Hydropyrolysis and pyrolysis at Strathclyde University in the fixed bed reactor and 2- Hydropyrolysis experiments at NewCastle University to look at the isomerisation of free cholestanol under these conditions. Obviously, in hydropyrolysis, we are hoping quantitatively release the cholestanol with little isomerization. The hydropyrolysis (with subsquent hydropyrolsis on the maturated resin) will enable us to compare isomerisation in the free and kerogen-bound forms for cholesteran. In order to prepare p-hydroxybenzyl ether of cholesterol three different methods were tried, p-hydroxybenzylchloride could not be used because of self polymerization of it. First method was preparation of p-hidroxybenzyl etherbeginning from p-methoxybenzyl bromide. Cholesterolsodium salt was formed and reacted with p-methoxybenzyl bromide synthesized from p-methoxy toluene with N- bromosuccinimid. The ether was formed with high yield but demetylation step was unsuccessful because of the formation of the resinous product. Demethylation was realized with pyridiniumhydrochloride at 200°C, probably at this condition benzyl- ether bond was also broken. In the literature, it couldn't find any stereoselective deprotection reagents for deprotection reactions i.e. selective compound for demethylation versus debenzylation reactions. H90 Reflux,,.,,^^ _ T " ^ (CH3)NaS04 DBP ? ca XIHO CH2Cl(Br) Benzen or THF/DMF CH30 ~©-CHb0 »? Cholesterol The second method was protection of phenolic hydroxyl group with benzoylchloride as ester. NaH + <Qkc-0-(P>-CH2C1 O THF/DMF <o^-°- o Formed product XllEsterification and bromination steps were successful but when the halo compound was reacted with cholesterol, undesired product was formed by trans esterefication reaction. The third method was protection of p-hydroxy benzaldehyde with THP. It was used as a protection group because THP ethers are stable under basic condition. In the second step of third method, reduction procedure by NaBEU was performed 4- (tetra-hydropyran-2-oxy) benzylalcohol. In the third step, p-toluensulfonation between TsCl with 4-(tetrahydropyran-2-oxy) benzylalcohol was occured 4- (tetrahydropyran-2-oxy) benzyltosylate. In the last step, we were tried to do etherification reaction between cholesterol sodium salt and 4-(tetrahydropyran-2-oxy) benzyltosylate. Desired product has not been obtained. HO-CHhO + 0 »r ^M^CHO r^\ S02C1 /\ CH3 Ts : p-tohiensulphonat Xlll° 0-^^-CH2OTs + NaH + HÖ THF/DMF No Reaction All this reaction steps were done succesfülly except the last one. At that reason, we had to use p-methoxybenzyl cholesterol ether instead of p-hydroxy- benzylcholesteryl ether to produce the aimed model compounds (co-resole). One mole 4-methoxybenzyl cholesteryl ether was reacted with 3 moles phenol and 3 moles formaldehyde. This co-resole shows similar properties like oceanic sediments (fossils sediment ). -S. 9H 9CH3 ?H ^ CH^ Jk. CH2 ^^CH2OCH2vJL^CH2 CH2 I O I Cholesterol ÇH2 XIV
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