An improved method for the preparation of diazonium salts was developed. Aliphatic diazonium salts were isolated for the first time. A method for their preparation was also worked out. The use of sulfonium salts as a route to deuteration of organic compounds was looked into

Picard, Geoffrey D.

English

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Union CollegeUnion | Digital WorksHonors Theses Student Work6-1975Sulfonium Salts, Aliphatic and AromaticDiazonium Salts, Formation and IsolationGeoffrey D. PicardUnion College - Schenectady, NYFollow this and additional works at: https://digitalworks.union.edu/thesesPart of the Chemistry CommonsThis Open Access is brought to you for free and open access by the Student Work at Union | Digital Works. It has been accepted for inclusion in HonorsTheses by an authorized administrator of Union | Digital Works. For more information, please contact digitalworks@union.edu.Recommended CitationPicard, Geoffrey D., "Sulfonium Salts, Aliphatic and Aromatic Diazonium Salts, Formation and Isolation" (1975). Honors Theses. 2119.https://digitalworks.union.edu/theses/2119SULFONIUM SALTS, ALIPHATIC AND AROMATIC DIAZONIUM SALTS, FORMATION AND ISOLATION by .,~ ~ Geoffrey D. Picard UC I q 15 111 ) ********* Senior Thesis Submitted in Partial Fulfillment of the Requirements for Graduation DEPARTMENT OF CHEMISTRY UNION COLLEGE JUNE, 1975 Ci tf 119oi, PS81ow 191$ c . ..:b J wish to thank John R. Sowa, without whose direction, understanding, and patience this research could never have been conducted. /fr ,f fl I 11 , I /I ;f// / t 0'--/J-- J/fl ·/~ pV/fi I ;//'/..._,, L> I , \ ii TABLE OF CONTENTS Abstract•••••••••••••·•~••••••$••••••••••••••••••••• iv Introduction •••••••••• ~••e•e••••••••••••e••~·••••••• 1 Experimental Preparation of Benzene Diazonium Bromide ••••• 4 Preparation of Benzene Diazonium Chloride •••• 6 Attemped Preparation of Benzene Diazonium Iodide ••••••• ~••••••••••••••••••• 7 Reaction between Berizene Diazonium Bromide and Diethyl Sulfide •••••••••••••• 8 Decomposition of Diethylphenyl Sulfonium Bromide in T~iglyme •••••••••••••• 9 Preparation of Aliphatic Diazonium Salts in Aqueous Solutions ••••••••••••• 10 Preparation of Aliphatic Diazonium Chlorides. 11 Preparation of Aliphatic Oxonium Chlorides ••• 12 Formation and Observation of Oxonium Ions •••• 13 Effect of Water on Reactions •••••••••••••••••••••••• 14 Results and Discussion•••••••••••••••••••••••••••••• 15 The Next Step•••••••••••••••••••••••••••••••e••••••• 19 BibliographY••••••••••••••••••••••••e••••••••••••••• 20 iii An improved method for the preparation of diazonium salts was developed. Aliphatic diazonium salts were isolated for the first time. A method for their preparation was also worked out. The use of sulfonium salts as a route to deuteration of organic compounds was looked into. iv Deuterated organic compounds are expensive. It was ~hought that they could be made less expensively by certain exchange reaction~. Deuterated compounds are used for spec- troscopic and kinetic studies. It is known that in the presence of base sulfl)nium salts undergo exchange reactions 1 1 + "'(' --- Dz 0 __ ) (Reaction 1) (RCDz) 3s + + HOD The purpose of this work then is to prepare a sulfonium salt that would have good solubility characteristics i,e., sol- uble in hot D20 and insoluble in cold D20. The salt should also thermally decompose to give a high yield of haloalkane. (Reaction 2) + Previous experiments have shown that aliphatic sulfonium salts do not recrystalize from D2o 2 Yhen the salts are decomposed in D20 other undesirable products such as the alco- 3 hol are formed • It was felt that the introduction of an aromatic group into the salts would improve on the solubility in addition to requiring less n2o in the exchange reaction. Sulfonium salts are characteristically made by the fol- lowing reactions. (Reactions 3,4,5) + so + 2 A1Cl2 + HCl 2 + 2 ROC6H5 (ROC6H4)3sc1 + HCl -·-----~ + HOA1Cl2 + + > + 5. + + + SO H 4 It was felt that perhaps aromatic sulfonium salts might be more easily made from diazonium salts in a neat reaction mixture. (Reaction 6) b. + - RN2 Br + R'-S-R" +· ... --~~ RR'R"S Br + (where at least one R is aromatic) Diazonium salts are prepared by several different methods. The most common and important method is the action of nitrous acid on primary amines. Almost any aromatic amine can be converted to a diazonium salt in the above way. Although the stability of the aromatic diazonium salts depends greatly on the anions present, their isolation is due to the stability of the cation Ph N2+o This stability is the result of the electron donating properties of the aromatic nucleus in the resonating system 4 • 3 Aliphatic diazonium salts have never been isolated because the instability of the saturated aliphatic residue I 'Nill not function as an appropriate electron donor. Although aliphatic diazonium ions are undoubtedly formed in solution they ionize immediately to the conjugate base; these bases have been detected in aqueous solutions 5 (Reaction 7) 7. -r - RR I CH-N=-"N x ~- ~---~' -HX - ~ ~ - RR' C-N N ~--)_,._ RR 1 C=N =N Nevertheless to extend the scope of this project the possible isolatiori of aliphatic diazonium salts ~as investigated. 'Preparation of Benzene DiazoniuD 3ro~ide A. To a 250-ml beaker sitting in a copper vessel and equip- ped for magnetic stirring was added 20g of ice and 20 ml of concentrated nitric acid. After the ice ~as permitted to melt the temperature was lowered to -10° by addition of liquid ni- trogen to the surrounding copper vessel. The mixture was stirred vigorously and 5g (.054 mole) of aniline was slowly added. The reaction mixture exothermed but ~as kept below -5°· A suspension of white to tan solid formed. Sodium nitrite (3g) was ground with a mortar and pestal to a fine powder and was added very slowly to the reaction mixture using a small spat- ula. To keep the temperature below -5° about 10 ml of liquid nitrogen had to be added to the outer vessel after each addi- tion. About 30 seconds was given between additions so that allthe sodium nitrite had reacted. When the tan solid dis- appeared the total addition was complete. This was confirmed by the starch-iodine test. B. To 100 ml of water saturated with sodium bromide was added about 3 ml of bromine. This was cooled to -5° and added to the above solution of diazonium salt. Although yellow orange crystals formed immediately the solution ·:;as stirred for 15 minutes to insure a complete reaction; Ttie r..-ixture was filtered through Whatman L1-0 fil tGr pafc..c· in a Bu c nne r funnel wh Lc h had been r;·_,~l::::d to o? .. Five grains of wet solici. (about .015 mole) 5 we r e obtained wh i.ch decomposed at about 7(} and was benzene diazonium tribromide. They were added to about 100 nl of acetone. Bromoacetone, a lacrymator, and 1.5g (.008 mole) of benzene diazonium bromid~ were obtained; -dee 105°;yield 18.5% 6 Preparation of Benzene Diazoniu~ Chloride To the solution of product of IA ~as added 100 ml of water saturated with sodium chloride and about 3 ml of bromine. This was cooled to -5° before addition. Al though ye Ll.ow green crystals formed immediately the solution was stirred.for 15 minutes to insure a more complete reaction. The mixture was filtered through Whatman Li-0 filter paper in a Buchner funnel cooled to o0 before filtration. Less than .lg of wet solid was obtained. This solid decomposed at 107° and was benzene diazonium chloride. ? Attempted Preparation of Benzene Diazonium Iodide Into a 250-ml beaker sitting in a copper vessel and equipped for magnetic stirring was added 20 grams of ice and 20 ml of concentrated nitric acid. After the ice was permitted to melt the temperature was lowered to ·-20° by addition of liquid ni- trogen to the surrounding copper vessel. The mixture was stirred vigorously and 5 g (0.054 moles) of aniline ~as slowly added. the reaction mixture exothermed but was kept blow -10°. A suspension of white to tan solid formed. Sodium nitrite (3.0 grams) was ground vii th a mortar and pest al to a fine powder an d was very s l ow Ly added to the reaction mixture using a small spatula. To keep the temperature belo~ -10° about 10 ml of liquid nitrogen had to be added to the outer vessel after each addition. Sufficient time was given bet~een additions, about 30 seconds, so that all the sodium nitrite had reacted. When the tan solid disappeared the total addition ·:;as complete. This was confirmed by starch iodide test. To 100 ml of water saturated with potassium iodide was added about 4 ml of bromine. This was cooled to -5° and added to the above solution of diazonium ion. Reddish brown crystals formed immediately and then decom- posed upon formation at -10°. The product of decomposition had a bp of 138° and was iodobenzene. The product was not soluble in water. 8 Reaction between Benzene Diazonium Bromide a'l.d Diethyl Sulfide Into a 50-ml round-bottom flask equipped with a condenser, magnetic stirring bar and an oil bath was added 1.5 g (.008 mole) of benzene diazonium bromide and 5ml (.056 mole) of diethyl sulfide. The mixture was heated overnight while stir- ring. Nitrogen was evolved and the mixture turned brown. The unreacted diethyl sulfide was evaporated on a Rotovap. 0 The residue weighed .5 g and melted at 120-130. It was soluble· in ethanol and acetone but insoluble in water. It was purified by precipitation from ethanol by the addition of water. One tenth gram (.0004 mole) of white crystalline diethyl phenyl sulfonium bromide was isolated, mp 118-120°; yield 5 percent. 9 Decomposition of Diethylphenyl Sulfonium Bromide in Triglyme Into a 50-ml round-bottom flask equipped with a conden- ser and heating mantle was added 20 ml triglyme, 2g (.002 mole) sodium bromide and 1.5g (.007 mole) diethylphenyl sulfonium bromide. A 25-ml round-bottom flask attached with a copper wire was submerged in liquid nitrogen and used as the collecting vessel. The mixture was heated to 200° for 1 hour. The collecting flask had tYo substances in it. One vrns liquid and one solid at -1 96°. The liquid boiled away at -180°, the boiling point of qxygen and the solid melted at -169° and boiled at -105°; the melting and boiling points of ethylene. 'The residue distilled (using the same set up) at 204° giving .5g (.004 mole) ethylphenyl sulfide (50 % yield). 10 Preparation of Aliphatic Diazonium Salts in Aqueous Solutions Into a 100-rnl beaker sitting in a copper vessel and equipped for magnetic stirring was added 10 ml of ~ater and 10 ml concentrated nitric acid. The ternperatu~e rras lowered to -25° by addition of liquid nitrigen to the surrounding copper vessel. The mixture was stirred vigorously arid 2-ml of butyl am i.ne was slowly added. The temperature rose to -20°., Sodium nitrite uee ground with a mortar and pestal to a fine powder and added very s LowLy , The mixture was kept at -20° by addition of about 10 ml of liquid nitrogen to the outer vessel after each addition... \Vhi te crystals formed and the solution turned pale blue from the presence of N2o3• The solid was not separated but the temperature was allowed to rise and decomposition took place with the evolution of ni-.~ , t 1 o O T..rogen a - 6. The crystals appeared to be butyl diazonium nitrate. l 1 Preparation of Aliphatic Diazonium Chlorides Into a 100-ml Erlenmeyer flask was added 20 ml dry ether and 2 ml RNH2, .R being methyl, ethyl, butyl, pentyl, or hexyl. The contents were cooled to -50° by lowering the flask into liquid nitrogen& Into another 100-ml Erlenmeyer flask was added 20 ml of dry ether and about 4g (.093 mole) nitrosyl chloride. This solution was slowly added to the first with vigorous stirring~ It was kept below -40° by lowering the flask into liquid nitrogen. Crystals formed immediately and the addition was complete when an aliquot was added. The ether was then poured away from the salt., Decomposition temperatures: -zoO -32° -J -24° -23° -20° -18° -15° 1 r 0 - 8 -10° _30 -50 -00 Methyl diazonium chloride; Ethyl diazonium chloride; Propyl diazonium chloride; Butyl diazonium chloride; Pentyl diazonium chloride, Hexyl diazonium chloride; The yields of all salts are greater than 75%. The butyl was as high as 9)%. 12 Preparation of Aliphatic Oxonium Chlorides Methyl, ethyl, propyl, butyl, pentyl and hex:yl diazonium chlorides prepared by the preceding method viex:e at.Lowe d to slowly war m to room temperature in dry ether. The ·.varming . process took about 30 minutes. During this time nitrogen was evolved and a solid with a new crystal structure was formed. At room temperature the solid settled to the bottom of the test tube. Some solid was taken out with a spatula and al- lo~ed to react with moist air~ The solids decomposed to a clear liquid that had an alcoholic odor. 13 Formation and Observation of Oxonium Ions Oxonium salts were produced by letting aliphatic diazonium chlorides decompose in dry ether. In all cases (methyl, ethyl, propyl, butyl, pen tyl, and hexy L. iiazonium ions) a ·:rhi te solid formed which settled to the bottom of the ether. If anhydrous rather t han practical grade ether .se ce used, more solid was formed. These reactions were executed at the decom- position temperature of each ion. (Reaction 8 ) + R2-·0--R + HOH ROH + It was observed that when the oxonium salts ~ere removed with a spatula and allowed to react with ~oist air they de- composed into a liquid without the evolution of N2• In all cases the liquid had an alchoholic odor. In the case of the products from methyl and ethyl diazonium ions the two distinct alcholic odors could be discerned. 14 Effect of Water on Reactions If there is an excess of water in the reaction mixture coupling reactions vrill occur. (Reaction 9) + N 2 + HCl + HO - r;;"\- N=N -//'\-~ \_/ ~/ These reactions are noted by the appearance of a deep blood red color along with the lack of ari appropriate amount of nitrogen. 15 The traditional method for the preparation of diazonium salts has been by the action ofnitrous acid on the primary amines. 6 The mechanism is 7 (Reaction 10 ) slow 2HONO ---}7 N 2o3 + · Ju:NH 2 + ----> + H Ar - ~ .:N-'01 H - - -H --------7 Ar~N-N=OJ H -· ----- .;-.. Ar-- N .::N --0- H Diazonium salts have probably not been extensively researched for they are thought to be too unstable and unpredictable for the average research student to explore. It was found that this is not the case. Rather, some of the traditional methods of preparation should be modified or changed completelye Griess 8 prepared the aromatic diazoniurn salts by using one mole of the mineral acid while the use of two moles is much better. This cuts down on the yield slightly 9 but the decomposition follows first order kinetics rather than that of the corresponding products of isomerisation with increasing pB. lO 16 Aliphatic diazonium salts have not been produced until now for their deco ,,,"JJ si tion points in aqueous media are usually below the freezing points of the solutions. In the scope of this work aliphatic diazonium salts have been produced in an aqueous mixture but extreme care must be taken to keep the temperature very low,usually at the melting point of the mixture, around -20c. The salts when produced this 'Nay are hard to isolate and therefore this preparative me t.hz.d is not desirable. 11 To expand the scope of this work nitrosyl compounds and the primarv amine were tried to produce the desired diazonium salt. 12 Dry ether and nitrosyl chloride were used. When the temperature of the mixture was lowered below o0 the aromatic diazonium salts were not produced but rather the nitroso amines and hydrochlorides of the aromatic amine. (Reaction 11) Ar-NH2 + NOCl + HCl + HCl + Ar·-NHz ----·'> Ar-NH3Cl The compounds must stay in solution long enough to change to the diazonium salts. At 20-40°c the aromatic amines in ether do form insoluble diazonium salts. The elevated temperature apparently allows the reaction between the nitroso compound and the hydrochloric acid to occur before precipitation; see 17 reaction10 The decomposition point of aromatic diazonium salts produced in this manner is over a very narrow range and vic<J-3nt, indicating their high purity. Aliphatic diazonium salts have never been isolated before. In this work aliphatic diazoniurn salts were produced in a non-aqueous environment. The physical and chemical behavior of the salts produced tend to support the assumption that they were truely aliphatic diazonium salts. The salts were colorless and when allowed to decompse in moist air turned into clear liquid with alcoholic odor. In the cases cif methyl and ethyl diazonium salts the corresponding alcohol has the appropriate odor of methanol and ethanol. (Reaction 12 ) +- - .R' - R11 ·• N .::N Cl + HOH R' -R"- OH + HCl + N 1' 2 The salts were also allowed to decompose in ether. This produced a change in crystaline structure with the evolution of nitrogen. The new products did not decompose when at temperatures of 25°c. 'I'he salts produced this way are believed to be oxonium saltse (Reaction 13) ..f- .R 1-:R"-NE!J Cl + :R--0-·R + R'-R"-0-R Cl R + N 1' 2 1 3 These oxonium salts were allowed to decompose in moist air. There was a change to a liquid without the evolution of nitrogen. Again an alcoholic odor was detected. (Reac- tion 1 Lt- ) -+- R r., R" - Q- R -=:1 + H-OH R i RI -R11 -OH + R-0- R + Hr'l v The temperatures of the reaction mixtures during the for- mation of the aliphatic diazonium salts could be lowered to -50°C due to use of ether and nitrosyl chloride. The lack of an aqueous solution also meant there ~ould be little or no OH- to replace the good leaving group (see reaction 9 ) From the Low decomposition points of these compounds and the evolution of nitrogen during decomposition along with their chemical behavior it can be deduced that the salts produced are aliphatic diazonium salts. 1 9 The Next Step Since the synthesis of diazonium chlorides, both aliph- atic and aromatic, have been dealt ~·ii th further work should be carried out to determine synthesis and characteristics of other anions. It should be relatively easy to use nitrosyl compounds such as the fl~ride and bromide to obtain respective diazonium salts, both aliphatic and aromatic. The reaction between diazonium salts and sulfides should also be .carried out using different reactor solvents, i.e. tetrahydrofuran, dioxane so as to find a sulfonium salt that ~ould be infinitely soluble in hot n2o and insoluble in cold D20. The synthesis of diethylphenyl sulfoniurn chloride would de a logical next step using benzene diazonium chloride and ethyl sulfide in THF. 20 BIBLIOGRAPHY 1. Rodd, Chemistry of.Carbon Compounds, Vol.IIIa, p. 266 2. Sowa, J,, R. , unpublished work 3. Ibid Li.. Weininger, S. , Contemporary Organic Chemistry, p. 507 D. Id Q ' R .nla ,uar-c. ~· (London), 15, p .. 435 6. Griess, P., Ann., 1858 pp. 106, 123 7. March, J., Advanced Orga.'1ic Chemistry, P~ 1+85 8. Ibid 9. Ridd, guar:_t .. Rev .. (London), 15, p , ~-30 10 • .Rodd, Chemistrv of Carbon Compounds, Vol.IIIa, p.,265 11. Ibid 12. March, J., Advanced Or~anic Chemistry, p .. 4.35 

Sulfonium Salts, Aliphatic and Aromatic Diazonium Salts, Formation and Isolation

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Sulfonium Salts, Aliphatic and Aromatic Diazonium Salts, Formation and Isolation

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