A Friedel-Crafts Alkyla

tionIntroduction:In order to produce an alkyl group atomic offspring 18ne, aromatic ring usually nethergo the Friedel-Crafts alkylation. This is usually d single in the armorial bearing of an alkyl halide with a Lewis biting catalyst. As limitations for this reception to consume place, the arene should be unsubstituted or should guard an activating meeting attached. such activating groups include: -OH, -OCH3, and -CH3 which submit extra resonance stabilization. Deactivating groups are electron withdrawing groups such as ?NO2. These withdrawing groups fail most of the age to station footfall to the prow this type of reception due to the leave out of resonance stabilization. In this reception the arene p-xylene is the starting aromatic compound. In this end the p-xylene is more(prenominal)(prenominal)(prenominal)(prenominal) reactive than the starting bodily, n-propyl chloride and aluminium chloride, so triplex shifts thot end take place. The p -xylene is present in lavishness to prevent multiple alkylations of the answer to take place. Rearrangements such as carbocation arrangements and methyl/hydride shifts house result in dissimilar alkyl arenes as crossroads. The alkyl halides, with an exception to methyl and ethyl, belowgo these rearrangements. Usually, under the Friedel-Crafts alkylation conditions, original alkyl halides rearrange to either secondary or tertiary carbocations that are much more horse barn. The reactant in this try out is n-propyl chloride. The products in this prove from the p-xylene are the unrearranged n-propyl group attached to the p-xylene (1,4-Dimethyl-2-n-propylbenzene) and the rearranged isopropyl group attached to the p-xylene (1,4-Dimethyl-2-isopropylbenzene). The aluminum chloride is the Lewis acid catalyst in the reaction and combines with the chloride ion of the n-propyl chloride to path the Friedel-Crafts complex. natural gunslinger chromatography will be utilise to square off the denary product distri savei! on of the resulting compounds. The purpose of this experiment is to carry out the Friedel-Crafts alkylation of p-xylene. besides the rearrangement of the primary alkyl group, n-propyl chloride, should be displayed. in the end the portion composition of each product should be opinionated by the gas chromatography results. It is expected that the 1,4-Dimethyl-2-isopropylbenzene will be form at a greater percentage due to the more lasting and thus faster isopropyl cation. The hydride shift speeds up the regale of this Friedel-Crafts alkylation reaction. answer Equation:Experimental Section:A 25 mL cps permeate flaskful was weighed, recorded, and 7.4 mL of wry p-xylene was added. The burdening of the flask was indeed reweighed and the weight of the p-xylene was determined by subtraction. The labialise seam flask weighed 23.68 g. The round bottom flask with the p-xylene weighed 32.25 g, so therefore the p-xylene weighed 8.57 g to start (.081 moles). A charismatic fling bar was added to the flask. A Claisen adaptor was attached to the round bottom flask, with a rubber cap at the one commencement and a calcium chloride drying tube attached to the opposite end. gainful carful attention 0.31 g of anhydrous aluminum chloride was weighed out and added to the reaction flask quickly. The aluminum chloride was added to the reaction flask under the punk very quickly because of its reactive nature with the atmospheric moisture. A conical ampul was weighed and 2.7 mL of 1-chloropropane of the source Aldrich was added. The vial was therefore reweighed and the amount of 1-chloropropane was calculated. The initial weight of the vial was 26.78 g and the weight of the vial and the 1-chloropropane was 28.99 g. By subtraction, the 1-chloropropane was weighed and recorded as 2.21 g (.028 moles). The 1-chloropropane was so added to the reaction flask drop wise with a syringe. The reaction flask was then left sit for an hour in contact with th e stir plate at means temperature. The smorgasbord! in the reaction flask during this hour was an orangish/ yellowed color. aft(prenominal) the period of an hour, 8.0 mL of water was added to the reaction flask. The addition of the water resulted in ovalbumin smoke. The flask was unploughed on the stir plate until the aluminum chloride was completely consumed. The mixture was then transferred to a 125 mL separatory displace and the bottom aqueous layer was discarded. The top layer was a milky white color while the bottom layer was get througher but not completely translucent. This process was completed again. Instead 5% aqueous sodium bicarbonate firmness was added to the seperatory funnel. This solution was added to the funnel in order to get rid of any more water present. The same separation appearance as the pace before was seen again. This process of separation was done at a time more with the addition of 6.0 mL of water added to the separatory funnel. After the lower aqueous layer was discarded, the rest of the solution was then transferred to a 25-mL Erlenmeyer flask. The flask was let sit for ten legal proceeding with occasional swirling, after(prenominal) 2.0 g of anhydrous sodium sulfate was added. The rest solution was then pipetted into a vial and a gas chromatogram of the product was obtained and analyzed. The same procedure was followed by a fissure bookman with 2-chloropropane as the alkyl halide and the gas chromatogram was obtained and analyzed. GC results: (GC of starting substantial attached)ComponentRT (min)%AreaStandard 1-chloropopane0.55100.00Standard 2-chloropropane0.4641.650.5258.35Standard p-xylene0.591.071.0198.93Product w/ 1-Chloropropane Product w/ 2-chloropropaneThe data obtained from GC outline of the products from the addition of 1-chloropropane were as follows:ComponentRT (min)%AreaComponent 10.610.73Component 21.0062.95Component 32.1315.31Component 42.3220.996The data obtained from GC analysis o f the products from the addition of 2-chloropropane w! as as follows:ComponentRT (min)%AreaComponent 11.0363.38Component 22.1236.62The Gas Chromatogram showed different results for two of the different reactants used. The GC for the 2-chloropropane showed the retention timed of the reactant, p-xylene, and the 1,4-Dimethyl-2-n-propylbenzene product. The GC for the 1-chloropropane that was used gave the retention genesis of the reactant, p-xylene, the 1-chloropropane reactant and the two thinkable products of 1,4-Dimethyl-2-n-propylbenzene and 1,4-Dimethyl-2- isopropylbenzene. Discussion:The gas chromatograms show decisive results. Comparing to the parameters of the p-xylene, 1-chloropropane, and 2-chloropropane the chromatograms of the resulting products were clear. For the GC of the reaction done with the 2-chloropropane there was a retention time of 1.03 for the p-xylene that matched up with the retention time of 1.01 of the given p-xylene. Also the retention time of 2.12 shown represents the 1,4-Dimethyl-2-isopropylbenzene t hat didn?t have to converge carbocation rearrangements with the 2-chloropropane as a reactant. The 1-chloropropane reactant chromatogram showed a retention time of 0.61 for the 1-chloropropane interconnected the 0.55 retention time of the given. The 1.00 retention time equals that of the given GC for the p-xylene. The two large retention times of 2.13 and 2.32 represent both of the products formed in this reaction with the 1-chloropropane as a reactant. some(prenominal) of the possible products showed up on this GC because of the carbocation rearrangement to produce more stability. The primary alkyl halide of 1-chloropropane underwent a carbocation rearrangement to speed up the reaction. both(prenominal) the 1,4-Dimethyl-2-n-propylbenzene and the 1,4-Dimethyl-2-isopropylbenzene are stand for in this GC. The prediction of rearrangement was proven. Mechanism: erst generated by the reaction of n-propyl chloride and aluminum chloride, the resulting Friedel-Crafts complex can put up with a hydride shift, breaking the carbon-ch! lorine bond and forming an isopropyl cation. This cation will eventually be attacked by a parlay bond from p-xylene. This forms a carbocation in the arene. The double bond is then reformed when the chlorine from the tetrachloroaluminate ion attacks the atomic bout 1 on the carbon of the isopropyl group. Conclusion:Through experimentation it was clear that the use of a different isomer of the reactant gave way to different products as seen with the help of the Gas Chromatogram. The process of Friedel-Crafts alkylation was carried out properly and the products of this reaction were well defined by the Gas Chromatogram results. The 1-chloropropane reactant, with electrophilic aromatic substitution gave way to the 1,4-Dimethyl-2-n-propylbenzene product and the rearranged 1,4-Dimethyl-2-isopropylbenzene. While the already stable carbocation once formed yielded the more stable product of 1,4-Dimethyl-2-isopropylbenzene. The rearrangement of the n-propyl chloride cation was dis played when the 1-chloropropane was used to form a more stable secondary carbocation product. References:MacKay, Elizabethtown College, department of alchemy and Biochemistry, A Friedel Crafts Alkylation. Modified 8/21/09O?Neil, Maryadele J. The Merck Index. fourteenth Ed. Merck & Co., Inc.: NJ, 2006. If you penury to get a full essay, order it on our website: OrderCustomPaper.com

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