Chemistry 35.1, University of the Philippines ManilaFull description
Chemistry 35.1, University of the Philippines ManilaFull description
Reaction of Alcohol Chemistry Laboratory Experiment 2012Full description
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Kondensasi aldol yang paling sederhana adalah gabungan dua molekul asetaldehid, yang terjadi jika larutan aldehid diberi larutan basa. Hasilnya adalah reaksi dengan 4 karbon dinamakan aldol(…Full description
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Experiment 1: Aldol Condensation Reactions Nam Na me: Avr vril il Wat atso son n Stu tude dent nt nu numb mber er:: 143 14302 0267 674 4 Objectives: The objectives ere ere s!lit into to "or this e#!eriment$ %irstl&' %irstl&' to s&nthesi(e diben(alacetone usin) the reactants ben(aldeh&de and acetone$ Secondl&' to calculate the amount o" aceto!henone re*uired re*uired to react ith 2$++) o" ben(aldeh&de to s&nthesi(e ben(alaceto!henone ,1'3-di!hen&l!ro!-2-en-1one. and in both cases to recr&stallise recr&stallise "rom ethanol$ Another objective o" this !ractical as to re"amilarise ourselves ith some lab techni*ues and calculations e learned in /unior %reshman hemistr&$ Theory: This !ractical as all about about aldol condensation reactions$ reactions$ An aldol condensation reaction is ver& im!ortant in or)anic chemistr& as it is a !er"ect a& to create carbon-carbon bonds$ %irstl& %irstl& an aldol reaction occurs ith the use o" the h&dro)en atom on an al!ha carbon$ At least one o" the reactants must have an al!ha h&dro)en or the reaction does not or$ t involves a reaction ith an enol or enolate ion to "orm an aldeh&de or a etone$ t is then deh&drated' resultin) in a conju)ated enone' i$e$ a double or tri!le bond se!arated b& a sin)le si)ma bond$ bond$ enerall& it "orms "orms an alene$ alene$ n the rst ste!s o" both o" these reactions' hen there there is aldol addition' the !roduct under)oes under)oes a loss o" ater made "rom the al!ha h&dro)en and the h&dro#&l )rou! "rom sodium h&dro#ide$ The ater lost is then used in the condensation reaction to re)enerate the 5- molecule "rom the base catal&st$ t is im!ortant to note that each condensation reaction must start start ith "ormation o" an aldol !roduct that can then be deh&drated to the enone$ The rst !roduct !roduct "ormed "rom "rom !art 1 o" the e#!eriment e#!eriment as diben(alacetone$ diben(alacetone$ This is a dimer o" ben(aldeh&de ben(aldeh&de and acetone$ The ben(aldeh&de ben(aldeh&de does not have an al!ha h&dro)en and there"ore it can onl& act as an acce!tor reactant' meanin) the acetone is the electro!hile in this reaction ,re" 1.$ suall& in aldol reactions there are 4 !roducts' but because one o" the reactants has no al!ha h&dro)ens it can onl& mae 2 !roducts$ These to !roducts are a mi#ture o" stereoisomers$ The same !rinci!le a!!lies "or the s&nthesis o" ben(alacete!henone$ This is also a dimer made u! o" ben(aldeh&de and aceto!henone$ 8eltin) !oints are ver& use"ul in chemistr&$ The& )ive us an idea as to hether a com!ound contains im!urities or not$ t the the tem!erature tem!erature ran)e in hich a solid melts into a li*uid$ The meltin) !oint ran)e o" diben(&lacetone is 110-111 9 ,re" 2. and ben(&laceto!henone is 7-+ 9 ,re" 3.$ All o" the reactants used in the !ractical ere ;ammable and some ere sin irritants so it as im!ortant to ear )loves to !rotect our hands$ Sodium h&dro#ide h&dro#ide is classied as corrosive so earin) !rotective e&e ear as essential$ Procedure:
All essential a!!aratus as set u! accordin)l& to s&nthesi(e both diben(&lacetone and ben(&laceto!henone$ The !ractical as com!leted in to !arts$ %or the rst !art' a mi#ture o" sodium h&dro#ide ,40m<= 28. and ethanol ,30m<. as made in a clonical ;as$ To a se!arate beaer' ben(aldeh&de ,2$77m<. and acetone ,1m<. ere added$ al" o" the ben(aldeh&de and acetone mi#ture as added to the clonical ;as ith the sodium h&dro#ide and ethanol in it$ The contents ere sirled and le"t alone "or 1 minutes$ A"ter the 1 minutes ela!sed' the remainin) mi#ture in the beaer as added to the clonical ;as$ This as then sirled a)ain and le"t "or a "urther 30 minutes$ n the meantime' the calculations ere com!leted "or the second !art o" the e#!eriment and the same a!!aratus set u! "or the s&nthesis o" ben(&laceto!henone$ The same a!!roach as the !revious !art as taen$ A mi#ture o" sodium h&dro#ide ,40m<= 28. and ethanol ,30m<. as made in a clonical ;as$ n another beaer' ben(aldeh&de ,2$77m<. and aceto!henone ,3$1m<. ere mi#ed$ al" o" this mi#ture as added to the clonical ;as' sirled and le"t "or 1 minutes$ A"ter 1 minutes' the remainin) mi#ture as added to the clonical ;as' sirled and le"t sit "or a "urther 30 minutes$ A"ter both mi#tures ere le"t "or 30 minutes the& ere dried o> usin) a vacuum ltration$ ?ach !roduct as !laced into its on @uchner "unnel and suced dr&$ When each !roduct as dr&' it as ashed ith 3 ali*uots o" deionised ater ,3# 60m<.$ The cr&stals "ormed in each case ere recr&stalli(ed b& dissolvin) each set in ethanol and usin) heat "rom the hot !lates$ @oth solutions ere then !laced in an ice bath and scratched until cr&stals "ormed$ @oth solutions ere then suced dr& a)ain usin) a vacuum ltration a)ain$ The dried cr&stalline !roducts ere ei)hed and the meltin) !oint ran)es determined "or each solid$ The !ercenta)e &ield as then calculated be"ore cleanin) and tid&in) aa& all )lassare used in the e#!eriment$ Results:
roduct @: Bield: 3$72) ercenta)e &ield: 60$74D ,be"ore recr&stalli(ation. EEFFF made a "e mistae throu)hout the lab hich le"t me ith no valuable results$ These results are m& nei)hbour iara 5G %l&nnGs results$ We ran out o" time be"ore e could recr&stalli(e the !roduct and obtain the meltin) !oint ran)e "or roduct @$ ill tal about this "urther in m& discussion on the e#!eriment$FFFEE Discussion: made a "e errors in the !ractical hich le"t me ithout m& on results$ 8& rst mistae occurred hile recr&stalli(in) !roduct A ith ethanol$ While
tr&in) to ash the !roduct "rom the inside alls to tr& and )et as much !roduct in as !ossible' thin used too much ethanol$ The solution as a trans!arent &ello colour hen it should have been a cloud& &ello colour$ ma& have over diluted the solution hich in turn a>ected the re"ormation o" cr&stals$ No cr&stals "ormed at all even ith a lot o" scratchin)$ The second error made as ith the "ormation o" cr&stals in !roduct @$ Hurin) the 1 minute aitin) !eriod a"ter addin) the rst hal" o" the ben(aldeh&de-aceto!henone solution' accidentl& thre out the other hal" hile tr&in) to clean as ent alon) ith the e#!eriment$ oever' didnGt realise until it as too late to # the !roblem$ There as not enou)h o" the ben(aldeh&de-aceto!henone solution to mae the reaction tae !lace$ This resulted ith no oil at the bottom o" the ;as and hence no cr&stal "ormation$ nstead as advised to evaluate m& nei)hbourGs results$ The e#!eriment too a lot lon)er than e#!ected$ The !ercenta)e &ield o" the !roduct A is ver& ver& lo$ This could be a result o" numerous errors that occurred throu)hout the e#!eriment$ 5n a "e occasions' the vacuum ltration suced bac resultin) in the loss o" some o" roduct A$ Also' durin) recr&stalli(ation' a sli)ht e#cess o" ethanol ma& have diluted the solution too much as the cr&stals that "ormed ere ver& small hich also e#!lains h& the !ercenta)e &ield as *uite small$ The meltin) !oint is also not as accurate as e e#!ected$ tGs not too o> but in theor& it should have been 110-111 9 hen it as actuall& C+-102 ℃ $ This is !robabl& due to im!urities still le"t in the sam!le due to inade*uate ashin) ith deionised ater and also !erha!s the e#cess o" ethanol$ There asnGt necessaril& an& errors made "or !roduct @ e#ce!t "or the "act that e ran out o" time to nish the e#!eriment$ This resulted in a reasonable !ercenta)e &ield that !robabl& ould have been a )ood bit loer minus the im!urities le"t in the sam!le$ Gd also e#!ect the meltin) !oint to be loer than hat it is accordin) to the literature value because o" these im!urities$ The calculations ere "airl& strai)ht "orard and eas& to do$ The& can be seen at the bac o" this re!ort$ Conclusion: 5verall' this as a ver& educational e#!eriment$ t re"reshed m& memor& on ho to conduct aldol reactions$ The to !roducts ere success"ull& s&nthesi(ed and an& errors made ere noted and understood$
