HOBWwBfiwBflEt 1 '..., ;;;••.:•• |nraffl{ -;:!; ffiffl < In ffi X I B RARY OF THE U N IVERSITY Of ILLINOIS 8. 547 UGs 965-66 pt.l Return this book on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. University of Illinois Library WftrH 1917 L161— O-1096 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/organicsemi1965661univ ORGANIC SEMINAR ABSTRACTS I965-66 Semester I Department of Chemistry and Chemical Engineering University of Illinois SEMINAR TOPICS I Semester I965-I966 Preparation and Reactions of Perfluorothiocarbonyl Compounds Lennon H. McKendry 1 Organosilylalkali -Metal Compounds Marvin Coon. 10 Heterocyclic Aromatic Sulfur Compounds Adriane Gurak 17 Recent Advances in Polynucleotide Synthesis D. T. Browne 26 Olefin Induced Initiation of Free Radical Reactions Buren Ree 35 The Photochemical Lability of Aryl and Vinyl Esters . Robert J. Schacht : . 4U Optically Active Sulfoxides Ronald J. Trancik ......... 52 The Mechanism of Symmetrization of Organomercuric Halides Z. M. Holubec . 60 Cycloalkyne Intermediates Manley R. Johnston 69 Tetracyanoethylene Oxide and Related Epoxides Hayden Lipp 78 Hexaalkylbenzenes Mildred McDaniel 86 Reactions and Synthesis With Noble Metals Robert A. Gardiner 9k An Extended Hlickel Theory— Some Applications in the Field of Organic Chemistry Robert E. Cunningham, Jr 103 Study of Free Radicals by Flow Systems and ESR Dennis Chamot 112 Cyclodecapentaene s Kenneth Zahn 121 The Peroxide Oxgenation of Aromatic Compounds by Ionic Pathways Bill Foglesong 129 Structure Correlations by Gas Chromatography (The Kovats Retention Index System) Roy Swaringen 138 -2- Phosphoric Acid Ester Synthesis Carl L. Mampaey 146 Complexes of Aromatic Trinitro Compounds With Bases Jon Kapecki. 15k Oleandomycin: A Configurational and Conformational Model for the Macrolides Daniel B. Dixon 163 . - -1- PREPARATION AND REACTIONS OF PERFLUOROTHI.OCARBONYL COMPOUNDS Reported by Lennon H. McKendry September 27 3 I965 INTRODUCTION Until recently, very little work had been done with perfluorothiocarbonyl com- pounds. Middleton and others have now developed general preparations and have found that the reactions of these compounds are often different and always more vigorous than those of the corresponding perfluorocarbonyl compounds PREPARATION OF PERFLUOROTHIOKETONES A significant preparation of hexafluorothioacetone (60/0 yield) published by Middleton, Howard, and Sharkey 1 of duPont involves the reaction of bis(heptafluoro- isopropyl) mercury5 with sulfur vapor at k^0° The fluorine magnetic resonance spectrum of the resulting product consisted of a single unsplit signal, the infrared spectrum showed a broad thiocarbonyl peak between 7«5 and 9\i, and the mass spectrum gave a parent ion of m/e 1.82. CF3 CF3 S This reaction is reported to S o have wide applicability. kE- FC-Hg-CFvc wrr rv -> CFrv —rC — CFnw 4- HgFTTo-i? ^ > 2 3 3 + 2 Perfluorobutane-2-thione and 4- CF3 CF3 chloroperfluorobutane-2-thione have been prepared from bis(4H- T TT octafluoro-2-butyl) mercury and bis (4-chlorooctafluoro-2-butyl) mercury, respectively. At lower temperatures the combination of reagents produces di- and polysulfides as the only products , These can be defluorinated by means of triphenylphosphine to yield the dimeric 1,3- dithietanes of the corresponding perfluorothioketones, which in turn can be pyrolyzed to give the desired thioke tones in high yields „ Thus, in the preparation of hexafluorothioacetone, 2,2,4 ,4-tetrakis( trifluoromethyl) =l,3«dithietane is obtained as the dimer Middleton feels that the perfluorothioketone is initially formed but that it dimerizes in the presence of triphenylphosphine. It is remark (CgHg)gP (CgH,^) P p> j- i;i -j 3 ^ Soo^ CF3-C-CF3 able that triphenylphosphine removes the fluorine rather than the sulfur. A possible sequence for the cleavage of the disulfide involves the removal of fluorine by triphenylphosphine, leaving a highly reactive anion as an intermediate. An excess of triphenylphosphine must be used with polysulfides in CF3 F F. CF3 CF3 FS j^f3 S^ CF3 S — S CF3 CF3 S — ^CF3 £F< (^g) 2 CF3-8-CF3 + (C^H5)3PF2 ^ A/ "CF, order to remove the exi is sulfur as (CsH5J3P=S Another general route to perfluorothioketones discovered by Middleton and his . „ o „. -2- coworkers 1 involves the reaction of secondary perfluoroalkyl iodide s with refluxing phosphorous pentasulfide „ In this manner, octafluorobutane-2-thione was obtained in over 90$ yield from 2-iodoperfluorobutane. The mechanism for this reaction may S C F CFICF C F ~C-CF 2 5 3 -fflo^ 2 5 3 be analogous to that proposed by Severson and Brice 3 for the high temperature oxidation of perfluoroalkyl iodides to the corresponding acid fluorides. Free radicals are postulated as intermediates F CF3 I C 2F5 -C-I C 2F5 -C- 1 1 CF3 F III P2S5 P2S3 + s2 CF3 CF3 2(111) + S2 C 2Fs--C^-S—S—C—C2F5 1 F F IV S II IV ±^2» C 2F5 ' -C-CF3 2-Iodoperfluorobutane reacts with sulfu# at lower temperatures to produce IV Irradiation of IV in the presence of a higher boiling thiol yields V, which can be dehydrofluorinated with sodium fluoride to give octafluorobutane-2-thione. SH I IV + HSR» —» R'SSR + C 2F5 -C-CF3 F V -=^£->NaF " V c 2F5CCF3 + NaHF2 PERFLUORCTHIOACID FLUORIDES Earlier authors have reported the preparation and isolation of thiocarbonyl fluoride, but their results have been questioned 4 Several others have isolated the compound only in very low yields 5 ' 6 ' 7 Middleton and coworkers 1 have prepared thio- carbonyl fluoride successfully from thiophosgene in an over-all yield of 6Cffo a Thio- phosgene is first dimerized to tetrachloro-l^-dithietane 8 and then fluorinated with antimony trifluoride 8 The resulting product is pyrolyzed at 475-500° to thiocarbonyl fluoride o Side products in the fluorination process are 4~chloro-2,2,4-trifluoro-lj 3-dithietane VI and 4,4-dichloro-2 > 2-difluoro-l > 3-dithietane VII o Pyrolysis of VI and VII also yield thiocarbonyl fluoride isolable by distillation. Thiocarbonyl CI S F fluoride has been S S 9 ^v / I !j prepared by Sundermeyer and Meise >/\ y v T250 " in comparable yield by allowing S T the thiosphosgene to react with VT alkali metal fluorides at high S temperatures CI F S S U U A second method devised by \ /\ / . r c ^J.-i'-w. + JJ-u-J! ^i / \ / V 42.5° th 3 Pont grou inv oiV cc the CI S F high temperature reaction of VII tetrafluoroethylene with sulfur This reaction is very dependent upon the reaction conditions 9 and considerable amounts of trifluorothioacetyl fluoride 10 and bis (trifluoromethyl) disulfide can 11 form as side products . Martin has reported that thiocarbonyl fluoride is the major product if the reaction is carried out over activated charcoal. Middleton and his coworkers 1 have found that chloro- and bromofluoroethylenes also react with . „ -3- _ S S sulfur to produce the q CF2 = CF2 5000.^000 F-C-F + CF3 -C-F + CF3SSCF3 corresponding perfluoro- ^ " thioacid halides in ca. QCffo yield „ Thus, chloro- difluorothioacetyl fluoride is obtained from chlorotrifluoroethylene „ Although the mechanism for this reaction has not been studied , the formation of chlorodifluoro- thioacetyl chloride from l,l-dichloro-2,2-difluoroethylene and sulfur has led Middle- ton to suggest that an episulfi.de is formed, which then undergoes a rearrangement II CF2 = CC12 ^0 cfV=5-c-ci C1CF2CC1 Other general methods published by the CI du Pont group ai e . a) the reaction of normal perfluoroalkyl mercurials and sulfur, and b) the reaction of perfluoroalkyl iodides with phosphorous pentasulfide A special case is the reaction of ^,4-diiodoperfluoro-l-butene and sulfur , Sulfur reacts mainly at the site of the a. (CF3CF2)aHg -J§qo> CF3CF b. CF3CF2I -||§5* C F3CF iodine atoms and not at the double bond,, 12 „ S Harris and Stacey have caused various CF2 = CFCF2CFI 2 i c> CF2 = CFCF2CF perfluoroalkylthiols to react with sodium ^ fluoride to obtain the corresponding perfluorothioacid fluorides in good yields,, Thus, the reaction of 2-chloro-l,l,2- trifluoroethanethiol with sodium fluoride gave chlorofluorothioacetyl fluoride, S Chlorodifluorothioacetyl HC1CFCF2SH + NaF > HC1CFCF + NaHF2 fluoride was produced by Yarovenko, Motornyi, Kirenskaya, and Vasilyeva13 by reacting 2-chlorotetrafluoroethylsulfenyl chloride with tin in the presence of hydrochloric acid„ The required starting material14 had been prepared previously S CF C1CF SC1 CFsCICF + CFsClCFsSSCFsCFsCl 2 2 t£?~»HC1 (1^o) by chlorinating dichlcrooctafluorodiethyl disulfide PERFLUOROALKYLDITHIOESTERS AND PERFLUOROALKYLTHIOAMIDES The du Pont group1 have utilized the perfluorothioacid fluorides previously described for a general preparation of the perfluorodithioesters by allowing the acid fluorides to react with alkyl or aromatic thiols „ In this manner, ethyl tri- fluorodithioacetate and phenyl trifluorodithioacetate have been produced from, the reactions of ethyl mercaptan and phenyl mercaptan with trifluorothioacetyl fluoride «, Sodium fluoride must be present to remove hydrogen fluoride, a NaF n CF3CF + RSH ~^£^, CF3C-SR 4- NaHF2 R = CaH5 ,CeH5 The preparation of trifluoromethyl dithioesters is more complicated owing to the sodium fluoride catalyzed dimerization of these compounds , The dithioesters can be produced by pyrolyzing the dimeric 1,3-dithletanes at 600°. NaF CfJJF + CFnSH > CF3CSCF3 ^^> 6oq° )cT :f3 > cf3cscf3 S ?-SCF3 •I CF^SH CF3C-SCF3 -~?™* CF CH-SCF NaF 3 : , J4 . The reaction of 1,4-diodooctafluorobutane with phosphorous pentasulfide is a special case in which hexafluorodithiobutyrolactone VIII (25/0 yield) is formed. Compound VIII can also be s s produced by the reaction of I(CF I f^ 1 ) -4£&>1 X 2 4 500 520 hexafluorocy|.clobutanone and F2 phosphorous pentasulfide at F 2 520°. At lower temperatures VIII perfluoro-5 ,10,11-trithiadi- spiro[3.1o3.2]undecane (IX) and perfluoro-5 A°-dithiadispiro[3 lo3°l]decane (X) are produced. The former can be pyrolyzed to yield VIII.