FOREWORD
Ladies and gentlemen! Let me proudly introduce to you another story from Zealot’s dream collection. While there’s 11 steps in the synthesis, its longitude is explained by the fact that all the precursors and even some reagents are made from scratch, employing user-friendly techniues and euipment in fact, a need for vacuum is mentioned only once, and even that is for the removal of solvent"# as $ell as only easy-to-get reactants. %till the synth is obviously for the s&illed only# for one thing, it involves involves ma&ing a 'rignard. (here is a potential possibility to use )incorganic compounds instead discussed in detail beelo$" $hich is much cheaper and easier technically. technically. *lso there is added an alternate preparation of o-chloroben)onitrile o-chloroben)onitrile by )ealot. With this said, let’s get to business. - *ntoncho EX
PE R IM E N TAL
1. o-Chlorobenzoic acid
*nthranilic acid 1+,g
l conc., d/1,10"
a23 4g
ul 15g
1+,g anthranilic acid is stirred in a glass bea&er in 65mls $ater, $ater, 34mls l and 35g ice. With constant stirring and cooling there7s added 4g a2 3 in 65mls $ater. (hus obtained clear solution of dia)onium salt is very slo$ly added $ith stirring into a soln. of 15g ul in 38g l conc. * vigorous evolution of nitrogen is observed. When the rxn ends, the ppt is filtered, $ashed $ith cold $ater and reprecipitated from a. a 32+. (he product represents fine crystals and melts at 165-1619. o-:romoben)oic o-:romoben)oic acid can bee obtained in an analogous manner, substituting ul for u:r. 2. o-Chlorobenzonitrile Preparation A.
;22"3Zn < =b%"3 / 3 ; < Zn% < =b% < 3 2 3
(he best results are obtained $hen a )inc salt is employed instead of free acid. (his rxn is unsuitable for amino-, nitro- and oxy- acids, but can bee used for bromo- and chloroben)oic acids. (o a hot soln of 85g a2 in 655mls $ater there7s added 108g o-chloroben)oic acid. arefully neutrali)e $ith + or a2+ and add $ith heating 158g >8? excess" Zn%26 in 655mls $ater. (he precipitated salt is dried for prolonged time at 3559 and mixed intimately $ith 358g =b%" 3. (he mixture is coffeeground and dried at 135-1659 for a prolonged time, then heated on open flame - the mixture melts and gases are evolved. @istilled nitrile is treated $ith 62, steam-distilled and salted out. Aield 1+g 45?", mp 6+-6B9, bp 3+39. (he rxn usually ta&es place $ithin +5-B5 mins, but the duration of dryings ma&es the method uite time-consuming. Preparation B.
(his one doesn7t reuire a prolonged drying. %ulfaminic acid is dirt cheap and can bee acuired $ithout causing any suspicion. o-Bromobenzonitrile
85g o-:romoben)amide and +8g 38g/theory" sulfaminic sulfamic" acid is thoroughly mixed and heated in a Wurt) flas&. *t 385-3889 distillation begins, $hich is over at 348-3089 ta&es approx. 1.8-3 hrs". (he collected product is redistilled, yield +Bg 45? of theory". mp 8+-89, bp 381-38+9 As I found recently, this can bee simplified yet more, by forming benzamides in situ from the corresponding acid and urea..but since this is a very good route to subst’d benzaldehydes from benzoic acids, I’ll post it later separately. 3. Cyclopentanone
155g adipic acid and 15g :a2" 3 is intimately mixed and placed into a flas& $ith a thermometer. (he rxn is heated to 3459, the mixture initially melts and then the distillation ta&es place, $hich lasts about 1-3 hrs. (he hot distillate is saturated $ith al, the upper layer is decanted and distilled, collecting the fraction boiling at 134-1+59. @ry $ith Cg%2 6. AieldD 81g 40? of theory". Notes:
Ca(!"# may bee substituted for $a(!"# %ithout much loss in the yield. if one is to use pre&made Ca or $a adipinate, no temp control is necessary.
4. Aluminium isopropoxide
*li-=r2"+ - :p 1+5-1659 at mmg# mp 1149.
Ento a 385ml ;:F euipped $ith an efficient reflux condenser there7s added Bg *l foil, 5mls 81mls in theory" abs. E=* commercial reagent grade E=* $as used $ithout any drying" and 5,1g g%2 6. (he mixture is heated. En the beginning of boiling 5,8mls l 6 (CA!"#$% !xtremely toxic%& and heating continued until 3evolution starts, $hen it is stopped, sometimes even cooling7s needed. *fter the rxn subsides, heating is continued until almost full dissolution of *l 8- hrs". (he obtained solution is immediately used as is in the follo$ing preparation. '. Cyclopentanol
Ento a 385ml ;:F euipped $ith a 18cm Gigreux column and distilling condenser there7s added 8+mls 85g" cyclopentanone in 85mls E=* and the soln from the previous prep7n, $hich contains about 65g *l isopropoxide. (he rxn is gently heated, $hich causes acetone $ith some $ater to distill off. (he distillation is ended $hen the temp of the vapors rises to >489. (he ppt inside the flas& is carefully decomposed $ith 85? 3%26 until acidic and saturated $ith al. (he upper layer is decanted and distilled, collecting the fraction boiling at 1+-1659. @rying $ith Cg%2 6. AieldD 6g 06?" . Cyclopentylbromide
En a flas& there’s mixed 6mls 68g" cyclopentanol and B5mls 05g" 64? a. :r. 15g a3%26 is added. (he rxn is left for 36hrs $ith vigorous stirring. *fter that it’s diluted $ith 355mls $ater and the lo$er organic phase is separated and $ashed $ith $ater t$ice. @istill, collecting the fraction bet$een 1+-1+49. @ryed $ith Cg%26. Aield / 84g 6?" ). Cyclopentyl ma*nesium bromide
Ento a 385mls three-nec&ed flas& euipped $ith a reflux condenser, addition funnel and inert gas inlet there’s placed 85mls (F &ept over H2, prior to the rxn 185mls refluxed over +5g a2 for Bhrs and distilled". 0g of fine Cg turnings is added follo$ed by some iodine crystals. (he apparatus is flushed $ith argon and a gentle stream of gas is left flo$ing in. Cagnetic stirring is commenced. (he mixture instantly beecomes cloudy from CgE. From the addition funnel there’s dripped 88g 65mls" cyclopentyl bromide in 155mls (F so that the soln boils smoothly. (he rxn is usually over in an hour, it is accompanied by precipitation of a $hite Ielly-li&e mass, and at the bottom there maybee left some unreacted Cg as a dar&-grey po$der. Jsage of (F instead of ether is preferred since the rxn in it proceeds better and faster (F is a more specific solvent for 'rignards" , the yield is better as $ell. :eesides, (F can bee dried $ith a2, $hile for ether,sodium metal is usually employed. Notes on the possible usage of 'n&organics: .. Nitriles are not bad as electrophiles, so it is possible that despite smaller reactivity of 'n)#compounds, they %ould %or* e+ually %ell here & esp. if the rn conditions are made harsher (gentle reflu instead of )-".
/hat one CAN say for sure&is that the rn %ith 'n) # %ill go 0ust fine if one is to use o&chlorobenzoyl chloride instead of benzonitrile. !aloanhydrides generally are the best species for coupling %ith metalloorganics. $is&dicyclopentyl zinc is conveniently made from the corresponding bromide, no need to ma*e iodide here. And o& chlorobenzoyl chloride can bee easily prepared from o& chlorobenzoic acid (obtained in Step 1 " and 1Cl 2 or some such. +. o-Chlorophenyl cyclopentyl ,etone
(o the thus obtained 'rignard soln there’s added 64g o-chloroben)onitrile and the mixture is stirred for + days at ;(. Et is then poured into a mixture of iceK6l, $ith addition of some conc. a. + and left at ambient temp until all ice melts. (he &etone partially floats, partially goes to the bottom. Et’s extracted $ith ben)ene. (he yields fluctuate, but rarely drop beelo$ 88?. . alpha-Bromo-(o-chlorophenyl&-cyclopentyl ,etone
65g &etone is dissolved in 5mls l 6 and $ith cooling in sno$ it is added into a soln of 64g dioxane dibromide in 85mls dioxane, and stirred at ;( for +5mins. (hen +5mls $ater are added and the soln is $ashed $ith a32+ a. until neutral. (his may lead to some preciptation of the bromo&etone, $hich stays in l6. (he solvent is removed, giving 6g 48?" of the bromo&etone. 1. (1-hydroxy-cyclopentyl&-(o-chlorophenyl&-/-methyl,etimine
68g of the above bromo&etone is dissolved in 85mls ben)ene, add therein 85mls triethylamine 1gK3+mL is reuired for neutrali)ation of :r, but a 3x excess is used". (he soln is then saturated $ith 8g methylamine, obtained by dripping a saturated soln of 18g Ce3l onto 15g a2, dried thru a2. (he rxn is left for 1 day and the solvents are removed under aspirator vacuum, giving +5g 45?" of methyl&etimine. 11. 0etamine
15g of methyl&etimine is dissolved in 155mls undecane and boiled at 1089 for +-6hrs. Hetamine is extracted $ith 35? l. *cidic extract is basified and extracted $ith @C. %olvent is removed giving the product as an oil that uic&ly crystalli)es. Et can bee purified by recrystalli)ation from pentaneKether or hexaneKether. (he yields are close to uantitative.
Synthesis of Ketamine : Ketamine is more difficult to synthesize than the previously considered PCP derivatives. Although it is currently a popular and common drug on the illicit market, it is obtained exclusively by diversion of commercial sources rather than synthesis. This route has an overall yield of !"#, $ith a difficulty rating of %&' out of (" and a hazard rating of (&% out of (" ) ref. !*+. The general
necessity of producing anhydrous methylamine in a clandestine setting, rather than purchasing it, increases the difficulty. se of propylamine rather than methylamine $ould simplify this reaction, as its boiling point is above room temperature vs. methylamine, $hich is a gas at room temperature. The syntheis starts $ith the reaction of cyclopentyl -rignard and o& chlorobenzonitrile to give o&chlorophenyl&cyclopentyl ketone, follo$ed by alpha bromination of the ketone, and then reaction $ith methylamine to form an alpha&hydroxy imine )(&ydroxycyclopentyl&)o&chlorophenyl+&ketone&/& methylimine+. eating this imine results in Ketamine via a novel alpha& hydroxyimine rearangement ) refs. %", %(, %%, %', %* +. 0verall yields are !"#. Tiletamine is synthesized by an analogous process in industry, substituting %& thiophenyl magnesium bromide for the phenyl grignard and ethylamine for methylamine. T$o other ketamine analogs have been found on the black market1 the compound missing the %&chloro group on the phenyl ring, and its /ðyl analog. 2oth of these compounds are most likely more potent and longer lasting than ketamine.
Synthetic procedure for ketamine synthesis:
Step 1: (o-chlorophenyl)-cyclopentyl ketone
((3." g of cyclopentyl bromide and (3.* g of magnesium are reacted in ether or T4 to give a cyclopentyl -rignard reagent. The best yields are obtained if the ether solvent is distilled from the -rignard under vacuum and replaced $ith hydrocarbon solvent, such as benzene. 55.% g of o&chlorobenzonitrile is then added to the reaction mixture and stirred for three days. The reaction is then hydrolyzed by pouring it onto a mixture of crushed ice and ammonium chloride, containing some ammonium hydroxide. 6xtracion of the mixture $ith organic solvent gives o&chlorophenylcyclopentylketone, bp 3!&37 C )".' mm g+ )CA89 !7*"&:5&:+. Step 2: alpha-bromo (o-chlorophenyl)-cyclopentyl ketone
To %(." g of the above ketone is added ("." g of bromine in :" ml of carbon tetrachloride drop$ise at " deg. C. After all of the 2r% has been added, an orange suspension forms. This is $ashed $ith a dilute a;ueous solution of sodium bisulfite and evaporated to give (&bromocyclopentyl&)o& chlorophenyl+&ketone, bp (((&((* C )".( mm g+.
%3."g of above bromoketone is dissolved in 5" ml of li;uid methylamine freebase. 2enzene may also be used as solvent. After one hour, the excess li;uid methylamine is allo$ed to evaporate, although increasing the reaction time to *&5 days may increase yield. The residue is then dissolved in pentane and filtered. The solvent is evaporated to yield (&hydroxy&cyclopentyl&)o& chlorophenyl+&ketone /&methylimine, mp !% C )yield :*#+. Step : 2-!ethylamino-2-(o-chlorophenyl)-cyclohexanone (Ketamine)
The final step is a thermal rearrangement, and gives almost ;uantitative yield after (:" C for '" min. An alternative to the use of decalin as solvent in this step is to use a pressure bomb. %." g of the preceeding /&methylimine is dissolved in (5 ml of decalin and refluxed for %.5 h. After evaporation of the solvent under reduced pressure, the residue is extracted $ith dilute hydrochloric acid, the solution treated $ith decolorizing charcoal, and the resulting acidic solution is made basic. The liberated product, %&methylamino&%&)o&chlorophenyl+&cyclohexanone
)Ketamine+, after recrystallization from pentaneðer, has a mp of 3%&3'C. The hydrochloride has a mp of %!%&%!' C. As $ith PC6, the freebase is too caustic to be smoked, and must be converted into the Cl salt in order to be consumed in this manner.
/ext 8ection1 8tructure Activity =elationships of PCP Analogs 2ack to Contents
Hetamine7s hydrochloride salt is sold as Hetanest, Hetaset, and Hetalar. (he chemical structure bears absolutely no resemblance to common salts. (hough E don7t thin& home-based &etamine synthesis is realistic usually, &etamine is obtained from vet suppliers", here are the instructions, Iust for &ic&sD %tep 1D o-chlorophenyl"-cyclopentyl &etone 110.5 g of cyclopentyl bromide and 10.6 g of magnesium are reacted in ether or (F to give a cyclopentyl 'rignard reagent. (he best yields are obtained if the ether solvent is distilled from the 'rignard under vacuum and replaced $ith hydrocarbon solvent, such as ben)ene. 88.3 g of o-chloroben)onitrile is then added to the reaction mixture and stirred for three days. (he reaction is then hydroly)ed by pouring it onto a mixture of crushed ice and ammonium chloride, containing some ammonium hydroxide. Mxtracion of the mixture $ith organic solvent gives o-chlorophenylcyclopentyl&etone, bp 0B-0 5.+ mm g" *%N B65-48-4". %tep 3D alpha-bromo o-chlorophenyl"-cyclopentyl &etone (o 31.5 g of the above &etone is added 15.5 g of bromine in 45 ml of carbon tetrachloride drop$ise at 5 deg. . *fter all of the :r3 has been added, an orange suspension forms. (his is $ashed $ith a dilute aueous solution of sodium bisulfite and evaporated to give 1bromocyclopentyl-o-chlorophenyl"-&etone, bp 111-116 5.1 mm g". Aield is >BB?. (his bromo&etone is unstable and must be used immediately. *lso attempts to distill it at 5.1 mm g lead to some decomposition, so it should be used $ithout further purification. (he bromination may also be carried out $ith -bromosuccinimide in some$hat higher yields >?". %tep +D 1-hydroxycyclopentyl-o-chlorophenyl"-&etone--methylimine 30.5g of above bromo&etone is dissolved in 85 ml of liuid methylamine freebase. :en)ene may also be used as solvent. *fter one hour, the excess liuid methylamine is allo$ed to evaporate, although increasing the reaction time to 6-8 days may increase yield. (he residue is then dissolved in pentane and filtered. (he solvent is evaporated to yield 1-hydroxycyclopentyl-o-chlorophenyl"-&etone -methylimine, mp B3 yield >46?". %tep 6D 3-Cethylamino-3-o-chlorophenyl"-cyclohexanone Hetamine" (he final step is a thermal rearrangement, and gives almost uantitative yield after 145 for
+5 min. *n alternative to the use of decalin as solvent in this step is to use a pressure bomb. 3.5 g of the preceeding -methylimine is dissolved in 18 ml of decalin and refluxed for 3.8 h. *fter evaporation of the solvent under reduced pressure, the residue is extracted $ith dilute hydrochloric acid, the solution treated $ith decolori)ing charcoal, and the resulting acidic solution is made basic. (he liberated product, 3-methylamino-3-o-chlorophenyl"cyclohexanone Hetamine", after recrystalli)ation from pentane-ether, has a mp of 03-0+. (he hydrochloride has a mp of 3B3-3B+ . *s $ith =M, the freebase is too caustic to be smo&ed, and must be converted into the l salt in order to be consumed in this manner.
*nd here7s a supposedly more Ouser-friendlyO &etamine synthesisD 1. o-chloroben)oic acid. *nthranilic acid 1+,g lconc. d/1,10" a23 4g ul 15g 1+,g anthranilic acid is stirred in a glass bea&er in 65mls $ater, 34mls l and 35g ice. With constant stirring and cooling there7s added 4g a23 in 65mls $ater. (hus obtained clear solution of dia)onium salt is very slo$ly added $ith stirring into a soln. of 15g ul in 38g l conc. * vigorous evolution of nitrogen is observed. When the rxn ends, the ppt is filtered, $ashed $ith cold $ater and reprecipitated from a. a32+. (he product represents fine crystals and melts at 165-161 . 2-bromoben)oic acid can bee obtained in an analogous manner, substituting ul for u:r. 3. o-chloroben)onitrile. =reparation * ;22"3Zn < =b%"3 / 3; < Zn% < =b% < 323 (he best results are obtained $hen a )inc salt is employed instead of free acid. (his rxn is unsuitable for amino-, nitro- and oxy- acids, but can bee used for bromo- and chloroben)oic acids. (o a hot soln of 85g a2 in 655mls $ater there7s added 108g o-chloroben)oic acid. arefully neutrali)e $ith + or a2+ and add $ith heating 158g >8? excess" Zn%26 in 655mls $ater. (he precipitated salt is dried for prolonged time at 355 and mixed intimately $ith 358g =b%"3. (he mixture is coffeeground and dried at 135-165 for a prolonged time, then heated on open flame - the mixture melts and gases are evolved. @istilled nitrile is treated $ith 62, steam-distilled and salted out. Aield 1+g 45?", mp/6+-6B , bp/3+3 . (he rxn usually ta&es place $ithin +5-B5 mins, but the duration of dryings ma&es the method uite time-consuming.
=reparation :. (his one doesnPQRSTRUQt reuire a prolonged drying. %ulfaminic acid is dirt cheap and can bee acuired $ithout causing any suspicion. o-bromo-ben)onitrile. 85g o-:r-ben)amide and +8g 38g/theory" sulfaminicsulfamic" acid is thoroughly mixed and heated in a Wurt) flas&. *t 385-388 distillation begins, $hich is over at 348-308 ta&es approx. 1,8-3 hrs". (he collected product is redistilled, yield +Bg 45? of theory". mp / 8+-8o, bp / 381-38+o *s E found recently, this can bee simplified yet more, by forming ben)amides in situ from the corresponding acid and urea..but since this is a very good route to substPQRSTRUQd ben)aldehydes from ben)oic acids, EPQRSTRUQll post it later separately. +.yclopentanone. 155g adipinicadipic" acid and 15g :a2"3 is intimately mixed and placed into a flas& $ith a thermometer. (he rxn is heated to 345 , the mixture initially melts and then the distillation ta&es place, $hich lasts about 1-3 hrs. (he hot distillate is saturated $ith al, the upper layer is decanted and distilled, collecting the fraction boiling at 134-1+5 . @ry $ith Cg%26. Aield 81g 40? of theory". otesD - a2"3 may bee substituted for :a2"3 $ithout much loss in the yield. - if one is to use pre-made a or :a adipinate, no temp control is necessary. 6. *luminium isopropoxide. :p / 1+5-165PSV9 at mmg# mp / 114PSV9 Ento a 385ml ;:F euipped $ith an efficient reflux condenser there7s added Bg *l foil, 5mls 81mls in theory" abs. E=* commercial reagent grade E=* $as used $ithout any drying" and 5,1g g%26. (he mixture is heated. En the beginning of boiling 5,8mls l6 *;MFJL! Mxtremely toxic!" and heating continued until 3 evolution starts, $hen it is stopped, sometimes even cooling7s needed. *fter the rxn subsides, heating is continued until almost full dissolution of *l 8- hrs". (he obtained solution is immediately used as is in the follo$ing preparation. 8. yclopentanol. Ento a 385ml ;:F euipped $ith a 18cm Gigreux column and distilling condenser there7s added 8+mls 85g" cyclopentanone in 85mls E=* and the soln from the previous prep7n, $hich contains about 65g *l isopropoxide. (he rxn is gently heated, $hich causes acetone $ith some $ater to distill off. (he distillation is ended $hen the temp of the vapors rises to >48 . (he ppt inside the flas& is carefully decomposed $ith 85? 3%26 until acidic and saturated $ith al. (he upper layer is decanted and distilled, collecting the fraction boiling at 1+-165 . @rying $ith Cg%26.
Aield 6g 06?" B. yclopentylbromide. En a flas& therePQRSTRUQs mixed 6mls 68g" cyclopentanol and B5mls 05g" 64? a. :r. 15g a%26 is added. (he rxn is left for 36hrs $ith vigorous stirring. *fter that itPQRSTRUQs diluted $ith 355mls $ater and the lo$er organic phase is separated and $ashed $ith $ater t$ice. @istill, collecting the fraction bet$een 1+-1+4 . @ryed $ith Cg%26. Aield / 84g 6?" . yclopentyl magnesium bromide. Ento a 385mls three-nec&ed flas& euipped $ith a reflux condenser, addition funnel and inert gas inlet therePQRSTRUQs placed 85mls (F &ept over H2, prior to the rxn 185mls refluxed over +5g a2 for Bhrs and distilled". 0g of fine Cg turnings is added follo$ed by some iodine crystals. (he apparatus is flushed $ith argon and a gentle stream of gas is left flo$ing in. Cagnetic stirring is commenced. (he mixture instantly beecomes cloudy from CgE. From the addition funnel therePQRSTRUQs dripped 88g 65mls" cyclopentyl bromide in 155mls (F so that the soln boils smoothly. (he rxn is usually over in an hour, it is accompanied by precipitation of a $hite Ielly-li&e mass, and at the bottom there maybee left some unreacted Cg as a dar&-grey po$der. Jsage of (F instead of ether is preferred since the rxn in it proceeds better and faster (F is a more specific solvent for 'rignards" , the yield is better as $ell. :eesides, (F can bee dried $ith a2, $hile for ether,sodium metal is usually employed. otes on the possible usage of Zn-organicsD O.. itriles are not bad as electrophiles, so it is possible that despite smaller reactivity of Zn;3 compounds, they $ould $or& eually $ell here - esp. if the rxn conditions are made harsher gentle reflux instead of ;(". What one * say for sure-is that the rxn $ith Zn;3 $ill go Iust fine if one is to use ochloroben)oyl chloride instead of ben)onitrile. aloanhydrides generally are the best species for coupling $ith metalloorganics. :is-dicyclopentyl )inc is conveniently made from the corresponding bromide, no need to ma&e iodide here. *nd o-chloroben)oyl chloride can bee easily prepared from ochloroben)oic acid obtained in %tep 1" and =l8 or some such.O 4. 2-chlorophenyl"-cyclopentyl&etone. (o the thus obtained 'rignard soln therePQRSTRUQs added 64g o-chloroben)onitrile and the mixture is stirred for + days at ;(. Et is then poured into a mixture of iceK6l, $ith addition of some conc. a. + and left at ambient temp until all ice melts. (he &etone partially floats, partially goes to the bottom. EtPQRSTRUQs extracted $ith ben)ene. (he yields fluctuate, but rarely drop beelo$ 88?. 0. alpha-bromo-o-chlorophenyl"-cyclopentyl &etone. 65g &etone is dissolved in 5mls l6 and $ith cooling in sno$ it is added into a soln of 64g dioxane dibromide in 85mls dioxane, and stirred at ;( for +5mins. (hen +5mls $ater are added and the soln is $ashed $ith a2+ a. until neutral. (his may lead to some preciptation of the bromo&etone, $hich stays in l6. (he solvent is removed, giving 6g 48?" of the bromo&etone.
15. 1-hydroxy-cyclopentyl"-o-chlorophenyl"--methyl&etimine. 68g of the above bromo&etone is dissolved in 85mls ben)ene, add therein 85mls 1g/3+mls" is reuired for neutrali)ation of :r, but a 3x excess is used". (he soln is then saturated $ith 8g methylamine, obtained by dripping a saturated soln of 18g Ce3Xl onto 15g a2, dried thru a2. (he rxn is left for 1 day and the solvents are removed under aspirator vacuum, giving +5g 45?" of methyl&etimine. 11. Hetamine. 15g of methyl&etimine is dissolved in 155mls undecane and boiled at 108 for +-6hrs. Hetamine is extracted $ith 35? l. *cidic extract is basified and extracted $ith @C. %olvent is removed giving the product as an oil that uic&ly crystalli)es. Et can bee purified by recrystalli)ation from pentaneKether or hexaneKether. (he yields are close to uantitative. :en)ene is not a good organic solvent as it is carcinogenic, therefore E $ould suggest to use diethyl ether instead. E understand that ben)ene is $idely used solvent in the lab, ho$ever E suspect the persons utilising this method are probably not highly s&illed chemists nor have a proper laboratory in order to carry out purification thechniues to a very high standard, hence my suggestion.
