Esterification of 4-methyl-2-pentanol and Acetic Acid
Esterification of 4-methyl-2-pentanol and Acetic Aculeated by Dispersion and Spectre and Characterized by Infrared Spectroscopy
The extrinsic of this lab was to prosperously synthesize an ester from an alcohol and acetic aculeated. This exemplification used 4-methyl-2-pentanol delay increase acetic aculeated to fruit (1,3-dimethylbutyl) acetate as seen in Figure 1. The construction of acetic aculeated delay 4-methyl-2-pentanol and sulfuric aculeated was dispersioned, gathered, distilled and identified using IR spectroscopy. The ester had a fruity fume when conciliateed. The concretion of the ultimate emanation was 0.582g which gave a 34.6% render. The results conciliateed indicated that the ultimate emanation wined was the ester (1,3-dimethylbutyl) acetate due to the concordant association commands of C=O and sp3 C-H. The discuss why the percent render was low was owing the disposition of the reaction itself fruited ether and ester and some emanation was past through rise. For coming exemplifications, the regularity must be performed a lot quicker in dispose to secure the lowest quantity of emanation exhales.
Often in chemical labs, esters are artificially synthesized in dispose to fruit an likeness of a zest. An ester can be synthesized by the reaction of an alcohol delay a carboxylic aculeated. In this exemplification, (1, 3,-dimethylbutyl) acetate was fruited through increase acetic aculeated and 4-methyl-2-pentanol as seen in Figure 1. The limiting reagent in this reaction is 4-methyl-2-pentanol so the presumptive render of the ester emanation is subject on 4-methyl-2-pentanol.
Figure 1: Reaction of 4-methyl-2-pentanol delay increase acetic aculeated
For this reaction, the dispersion conciliate be utilized. Ebullition is applied delay a paroxysm bit, to concede the reaction to take-place. The gas rises and escapes from the plump foot flask and is then propitioused by the introduce condenser. The gas turns end into a clear and oozes end into the foot flask. In dispose to migrate incontrovertible junctions, the fruit confused rise to severed junctions. The denser lamina or the aqueous lamina conciliate be at the foot and can be migrated delay a pipette. The emanation of ether and ester was distilled to severed the ester owing esters keep inferior paroxysm meanings than the ether. In spectre, the matter delay the inferior paroxysm meaning exhales and reaches the introduce condenser. The propitious region concedes the gas to modify says from gas to clear which forces the clear to ooze end down the into the Hickman leader due to ruefulness. In this reaction, the (1, 3,-dimethylbutyl) acetate was severedd from an unrecognized ether by distilling into the Hickman leader. An IR spectrum of the ultimate emanation is inaugurateed to say the desired emanation by comparing the association commands of the dedicated values. If the IR peaks and associations are the selfselfsame as the dedicated, then the unadulterated emanation would be the ester. A percent render conciliate be fitted to assess the quantity of ester fruitd.
First, conciliate an void plump foot flask and meet the concretion. Add encircling 1.5mL of 4-methyl-2-pentanol in the flask and reweigh. Delay the 3mL of sleek acetic aculeated pretended, add sulfuric aculeated delay a paroxysm bit. Inaugurate dispersion delay the trappings inaugurateed in antecedent labs delay a introduce condenser robust to propitious the reaction. Ebullition the trappings for 60 to 70 minutes. Propitious the reaction construction and suitableness noted, add 2-3 mL of 5% aqueous sodium bicarbonate until carbon dioxide construction ceases. Transplant construction and totter arduous. Migrate the aqueous lamina and relate the disunion technique two excite occasions. Migrate as greatly introduce from the fundamental lamina by adding mean quantitys of sodium sulfate and let the reaction be for 10-15 minutes. Behind a week, transplant the reaction delay the ether and ester into a vial and inaugurate spectre. Inaugurate spectre for 15 minutes at aplump 180 to 200 oC. Conciliate and concretion the ultimate emanation. Inaugurate IR of starting reactants and emanations. Clean up stations and rate the percent render.
Results and calculations:
Table 1: Table of concretiones during exemplification
Mass of plump foot flask
Mass of flask and 4-methyl-2-pentanol
Mass of 4-methyl-2-pentanol
Mass of vial
Mass of vial and emanation
Mass of emanation
Theoretical render for (1,3-dimethylbutyl) acetate
= 1.68g of
Percent render: x 100%
x 100%= 34.6%
Figure 2: IR anteriorly spectre
Figure 3: IR behind spectre
Table 2: Values of IR for ester (1,3-dimethylbutly) acetate behind spectre
Values in cm^-1
C-O (Fingerprint Region, arduous to differentiate)
Discussion and Conclusion:
For this exemplification, the ester (1, 3-dimethylbutyl) acetate was synthesized from acetic aculeated and 4-methyl-2-pentanol. However, this is not a one reaction track owing of the tetrahedral comprised ordinary in esterification. The restoration of the acetic aculeated leads to a excite reactive electrophile. This causes a tetrahedral comprised in which there are two equipollent hydroxyl commands. Then one of the hydroxyl commands is eliminated, a regularity disclosed as tautomerism. This then gives introduce and ester as the ultimate emanations. The reaction was prosperous fruitd from dispersion but problems arose during the second constituent of this exemplification, spectre. The ester as-well had a very unconnected fruity fume.
This reaction is dispersioned owing ebullition acts as a catalyst for the reaction. In the reaction track, the region is increased, concedeing excite geometrical collisions delay the emanations and requires inferior activation motive. This can be seen as an illustration of the Maxwell-Boltzmann incurvation. This was performed uniformly by using the aluminum arrest at aplump 110 oC. Behind dispersion take-placered, a spectre trappings was used in dispose to clarify the ester from the ether. The paroxysm bit was pretended in dispersion and spectre in dispose to secure that the reaction did not overebullition and ignite the reaction. Paroxysm bits are repeatedly made from carborundum (carbon and silicon) which are chemically heavy and concedes keen edges for bubbles to fruit which conciliate not overebullition the rule. The matters in the reaction are concedeed to bubble excite calmly rather than flying paroxysm causing splatter and ruining the exemplification. The introduce condenser was used for twain in dispose to propitious down the reaction in dispose to bar igniteing of the reaction and ensuring that the emanation in the gas say harsh end into clear say. The discuss why anhydrous sodium bicarbonate was pretended was to secure that any leftover introduce was bewildered and the fostering lamina contained solely the fundamental junctions. This was performed a whole of three occasions to secure that minimal introduce was left, but some of the emanation leaked when tottern.
The meaning of spectre is to severed junctions inveterate on their paroxysm meanings. The reaction construction that contained ester and ether was to be distilled in dispose to conciliate the ester in the Hickman leader. However, behind letting the reaction be for a week, most of the ether exhaled and the construction was mainly ester. This explains why during spectre, the construction in the conical vial disappeared as most or all went into the Hickman leader. This can be seen in Figures 2 and 3. The IR of anteriorly and behind spectre keep concordant values, peaks, and the straight authoritative commands which indicates that the construction contained solely the ester. The IR spectroscopy of behind spectre shows that there is a C=O association aplump 1735.27 cm-1, and a sp3 C-H association aplump 2959.19 cm-1 which indicates that the junction shown is in-fact an ester and that the extrinsic was met past ester do keep C=O associations aplump 1750 cm-1 and sp3 C-H associations aplump 2900 cm-1 . Ideally, the spectre regularity should be suited in isolating the unadulterated emanation, by concedeing the ester molecules to be in a gaseous exposure. Equilibrium conciliate be customary and concedes the molecules to fruit end into a clear exposure in the Hickman leader, but in this exemplification spectre was not inevitable. This right caused excite chances of losing the ester by not easily wining all the clear from the Hickman leader or by spirituous.
The results rendered a 34.6% render which suggested that there were deceptions delayin the reaction. One important discuss as to why the render was low was owing of the disposition of the reaction itself. The ether and ester in the conical vial was left to be for a week. Owing the ether had a inferior paroxysm meaning than ester, most or all of the ether exhaled due to elevated inconsistency at margin region. In restoration, the ester as-well has a elevated inconsistency but inferior than the ether owing of the construction and the force of the intermolecular forces. The ester has two oxygen atoms when-in-fact the ether has one oxygen resulting in inferior van der Waal forces. The ether was created as a byemanation which artful the apex quantity of render of ester fruitd. Therefore, not all the reaction take-placered to fruit an ester owing during that occasion there were junctions that hindered the apex quantity of render fruited by fruiting a track for the ether. This was from the sulfuric aculeated reaction arrangement to fruit an ether. The sulfuric aculeated dissociates into a proton and a bisulfate ion which fruits delay the OH command of the alcohol. The alcohol’s oxygen is protonated which fruits an oxonium ion. The ion decomposes to carbocation and introduce and the carbocation reacts delay another alcohol command to fruit another oxonium ion. The ion loses a proton to stabilize and fruits an ether. If a stronger alcohol, possibly 1-hexanol was used, a elevateder render would be wined owing the stronger intermolecular forces concedes the reaction to keep inferior inconsistency and the ester and ether fruited would as-well exhale suppress. Owing there are weaker van der Waal forces in the (1, 3-dimethylbutyl) acetate owing of the inferior carbon manacles, excite of the emanation was exhaled and past. In dispose to secure that a elevateder render is wined, the dispersion and spectre regularity must be performed end to end or a lot quicker anteriorly the ester and ether exhales at margin region. As-well an alcohol delay a longer carbon manacle should be used as stronger intermolecular forces concede excite ester to fruit.
While transporting the fundamental laminas and excite rise, some of the emanation was past. Even though this fountain of deception is minimal, there were some emanation past parallel the way by transporting through vials which artful the render of the ultimate emanation. Dispersion is an potent technique that concedeed Fischer esterification to take-place. Spectre is a very suited technique, but should not be applicable when one of the matters exhales due to elevated inconsistency. For coming exemplifications, the reaction must be performed greatly quicker in dispose to secure that the lowest quantity of ether and ester exhales and is past throughout the regularity and excite definite instruments can be used to gather the fundamental lamina. IR should quiet be used to differentiate the individuality of the emanation. Owing of the disposition of the reaction itself, a render suppress to the presumptive is very opposed to win, a realistic arrival would be aplump 60% render.
MSDS of (1,3-dimethyl butyl) acetate.
http://www.chemicalbook.com/ChemicalProductProperty_EN_CB8373308.htm (accessed November 7, 2014).
MSDS of 4-methyl-2-pentanol. http://www.sciencelab.com/msds.php?msdsId=9926088
(accessed November 7, 2014).
Padias, Anne.Making the Connections. Hayden McNeil, 2011.