Chemistry Extended Essay Essay Example for Free

alchemy Extended Essay EssayTo investigate the effect of 2-bromo-2-methyl propane do apply and temperature of the system on the stride of response of solvolysis of 2-bromo-2-methyl propane in 90% ethyl alcoholD nonpareil by Habib Is throw outdar HinnFriends Boys SchoolJune 22, 2007To investigate the effect of 2-bromo-2-methyl propane niggardliness and temperature of the system on the value of reaction of solvolysis of 2-bromo-2-methyl propane in 90% ethyl alcoholIntroductionThe major ingathering of the solvolysis of t -butyl chloride in 70 % urine 30 % dimethyl ketone is t-butyl alcohol, with a sm entiretyly amount of isobutylene being organize as a by productAnd this is with accordance of first order kinetic and suggests a ii step machine in which the set out determining step consists of the ionization of t-butyl chloride, and in this mechanism a carbonium ion is formed as inter- mediate and this bonds direct to near by nucleophile (in this wooing nucleophile is a neutral molecule) the initial product is t-butyl carbonium ion. Note1 if the nucleophile is neutral the product pass on be charged since the leaving group subscribe tos both bonding electrons away with itSo chemists have proposed to commonplace types of mechanism1- Nucleophilic substitution Sn1The ionization step in a Sn1 reaction is end separatemic and much sulky than the exothermic neutralization of carbonium ion by a nucleophile. And so the rate determining step being the unimolecular ionization of the t-butyl chloride compare 4, and as a result, the everyplaceall rate of reaction is not affected by trades in the concentration or kinds of nucleophilic reagents present.Note2 the constituent which determines the mechanisms employed is typically the nature of the substrate it self and not the specific nucleophileNote3 if the sum of the brawn of the product is lower than the energy of the reactant the reaction is exothermic, and if the product have higher energy than th e reactant the reaction is endothermic.2- Elimination E1 (elimination unimolecular)And because t-butyl chloride acts as a Lewis acid (an electrophile) and combines with a nucleophile to give a substitution product, so the major product of the solvolysis of t-butyl chloride in water-acetone dissolver is t-butyl alcohol.(Note4 electrophile an electron deficient atom, ion or molecule that as family relation beam for an electron bracing, and get out bond to a base or nucleophile.)(Note5 nucleophile and atom, ion , or molecule that has an electron pair that may be donated in forming covalent bond to an electerophile.)Evaluating the mechanismThe single reactant that is on a lower floorgoing change in the rate determining step is t-butyl chloride and so such reactions is a unimolecular and follow a first order equation (Sn1, E1). This means that the rate of the reaction varies directly with the concentration of t- butyl chloride. And since nucleophilic only participate in the fast atomic yield 16 step, so their relative molar concentrations rather than their nucleiophilities are the primary product determining factor, and by using nucleophilic root like water, so its high concentration will assure that alcohols are the major product, and because water have a high dielectric constant (e=81) so water molecule tend to manoeuver them-selves in such a way as to decrease the electrostatic forces between ions. And an important factor is the salvations which refer to water molecules ability stabilize ions by encasing them in a sheath of weakly bonded solvent molecules1- Anions are solvated by hydrogen bonding,2- Cations are solvated by nucleophilic sites on water molecule (oxygen). And in this case of t-butyl carbonium ion the nucleophiles form strong covalent bond to carbon and converting the intermediate to a substitution product.The reaction mechanism is a sequential account of each transition state and intermediate in a amount of money reaction, the over al l rate of reaction is determined by the transition state of highest energy in the sequence, so the rate determining step is the rate determining step for both the Sn1 and E1 for t butyl chloride.(Note 6 the water soluble organic solvent acetone is used to keep a reasonable concentration of t-butyl chloride in base)The balance equation for t-butyl chloride solvolysis in water-acetone solvent isThe effect of concentration on the solvolysis of t-butyl chloride in 70 %water 30 %acetone solvent.As the reaction proceeds the ascendant becomes increasingly acidic until all of the t -butyl chloride has reacted and all HCl that can form has formed. So we will monitor the reaction by allowing HCl formed to neutralize a predetermined amount of NaOH. An indicator dye (bromo-phenol blue) will change color when the NaOH has been neutralized, and conviction of the reaction should begin at the instant.So according to kinetic measurementsRate of reaction = K t butyl chlorideWhere K is the spec ific rate constant in S -1 and t butyl chloride is the concentration of t-butyl chloride in M.Our kinetic measurement will depend on the determination of the amount of HCl produced by the reaction, so by monitoring the color change of the acid base indicator, we will determine the clock time required for 10% of t-butyl chloride to hydrolyze by having 10 % as much NaOH present as T-butyl chloride.Rate = d Rcldt Where Rcl =-dt Rcl = K RcldtRearranging,d Rcl = -K dtRclAnd integrating for t=0 to t=t will give=Ln Rcl t Ln Rcl 0 = Kt 2.303 Log Rcl 0 = KtRcl t2.303 Log Rcl 0 = KtRcl tWhere Rcl 0 is the molar concentration at time t = 0Rcl t is the molar concentration at time t = tTwo methods to cypher K1- since the equationKt = 2.303 Log Rcl 0Rcl tIs an equation of a peachy line (y=mx+b) with hawk k. and intercept =0, a plot of 2.303 instal down Rcl 0 / Rcl t versus t should yield a straight line with slope k.2- if the solvolysis reaction run to 10% completionThen,Rcl = 0.90 Rc l 0Kt = 2.303 Log Rcl 0 = 2.303 log (1.11)0.90 Rcl 0And therefore,K = 0.104TSo by conclusion the value of K and compensate it in the rate of reaction equation Rate = KRcl where the concentration of Rcl is known we can portend the value of the rate of reaction and we will see its effect on the solvolysis of t butyl chloride in 70% water 30 % acetone result.The effect of temperature on the solvolysis of t -butyl chloride in 70%water 30%acetone solvent.In nearly every instance an increase in temperature causes an increase in the rate of reaction, because the total ingredient of all of the t butyl chloride 1molecules having energies equate to or greater than activation energy (Ea)Corresponds to the shaded portion of the area under the curve increases by increasing the temperature and by comparing the area for devil different temperature, we see that the total fraction of t- butyl chloride molecules with sufficient kinetic energy to undergo reaction increases with increasing te mperature and consequently, so does the reaction rate.Note7 changing the concentration affects the rate of reaction changing the temperature affects the rate constant as well as the rate.By knocking the values of reaction rate constant K for different concentration of t-butyl chloride and different reaction temperature, we will find the effect of temperature on the solvolysis of t-butyl chloride in water acetone solvent.Quantitatively, K (s-1) is related to Ea and T by the equationK1 = Ae-Ea/RT1 1Ea is the activation energy, in joule / mole. (Jmol-1)A is a proportionality constant, in s-1R is the gas constant = 8.314 Jmol-1K-1e is the base of the natural logarithms.T is temperature in Kelvin.This relation ship is known as Arrhenius equationWe measure Ea by taking the natural logarithm of eq.1Ln K = ln A EaRTThus, a plot of ln k versus 1/T gives a straight line whose slope is equal to -Ea/R and whose intercept with coordinate is ln ANote8 Ea is the activation energy, a constant ch aracteristic of the reactionWe can calculate the rate constant at some specific temperature if Ea and K at some other temperature are known.For any temp. T1 (known), Ea (known), K1 (known)K1 = A e -Ea/RT1For any other T2 (known) (K2 unknown)K2 = A e -Ea/RT2By dividing K1 over K2K1 = A e -Ea/RT1K2 A e -Ea/RT2Taking natural logarithm of both sides, we getLn K1 = Ea (1/T2 1/T1).K2 ROr in common logarithms (base 10 logarithms) givesLog K1 = Ea (1/T2 1/T1)K2 2.303 RAnd by finding the value of K2 we will be able to find the rate of reaction at T2 and we will find the effect of temperature on the rate of solvolysis of t butyl chloride in 70 % water 30 % acetone firmness.By finding the values of reaction rate constant K for different concentration of t-butyl chloride and different reaction temperature, we will find the effect of concentration and temperature on the solvolysis of t-butyl chloride in water acetone solvent.Procedure fibre A the effect of concentration on the rate of solvo lysis of t butyl chloride in 70%water 30%acetone solvent.a-Experimental procedure to measure the time necessary for 10 % solvolysis of t butyl chloride (0.1 M concentration) in 70 % water 30% acetone solvent at room temperature.A, a, I-1- typeset vitamin D ml of 0.1 M t- butyl chloride in acetone only and frame up it in an Erlenmeyer flaskful and tick off it 1.2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer and recording differentiate it 2.3- Using a burette take 30 ml of the solution in flask 1 and put it in another Erlenmeyer and recording label it 3.4- By a graduate pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it 4.5- Using a calibrated piston chamber measure 67 ml of distilled water added to an Erlenmeyer flask 4.6- conduct two drops of Bromo-phenol blue indicator to flask 4.A, a, II-1- summarize quick the solution in Erlenmeyer flask 4 to solution in flask 3 and start the pulley-block watch to cou nt for time in seconds.2- Swirl the mixture and after one or two seconds immediately pour the combine solutions back into Erlenmeyer flask 4 to minimize the errors in the results.3- The color of the commingle solutions is blue, so continue swirling the solution in Erlenmeyer flask 4 till the instant color of the solution start changing to yellow, hence we let on the getwatch and record the time.4- Repeat the procedure at to the lowest degree three times and calculate the average.5- Tabulate the results in record A.b-Experimental procedure to measure the time necessary for 10 % solvolysis of t butyl chloride (0.2 M concentration) in 70 % water 30% acetone solvent at room temperature.A, b, I-1- Prepare 500 ml of 0.2 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it 1.2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer flask and label it 2.3- Using a burette take 30 ml of the solution in Erlenmeyer flask 1 and put it in another Erlenmeyer flask and label it 3.4- By a graduated pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it 4.5- Using a graduated cylinder measure 67 ml of distilled water added to an Erlenmeyer flask 4.6- Add two drops of bromo-phenol blue indicator to Erlenmeyer flask 4.A, b, II-1- Add promptly the solution in an Erlenmeyer flask 4 to solution in flask 3 and start the stop watch to count for time in seconds.2- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into an Erlenmeyer flask 4 to minimize the errors in the results.3- The color of the motley solutions is blue, so continue swirling the solution in Erlenmeyer flask 4 till the instant color of the solution start changing to yellow, then we stop the stopwatch and record the time.4- Repeat the procedure at least three times and calculate the average.5- Tabulate the results in record A.Part B the effect of temperature on the rate of solvolysis of t b utyl chloride in 70%water 30%acetone solvent.a-Experimental procedure to measure the time necessary for 10 % solvolysis of t butyl chloride (0.1 M concentration) in 70 % water 30% acetone solvent at correct Celsius degree.B, a, I-1- Prepare 500 ml of 0.1 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it 1.2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer flask and label it 2.3- Using a burette take 30 ml of the solution in Erlenmeyer flask 1and put it in an Erlenmeyer flask and label it 3.4- By a graduated pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it 4.5- Using a graduated cylinder measure 67 ml of distilled water added to Erlenmeyer flask 4.6- Add two drops of bromo-phenol blue indicator to Erlenmeyer flask 4.B, a, II-1- Suspend the Erlenmeyer flasks in a water bath full with ice and water, allowing the temperature of the Erlenmeyer flasks and their contents to change state for t en minutes.2- Adding quickly the solution in Erlenmeyer flask 4 to solution in Erlenmeyer flask 3 and start the stop watch to count for time in seconds.3- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into Erlenmeyer flask 4 to minimize the errors in the results.4- The color of the solution after that will become blue, so continue swirling the solution in Erlenmeyer flask 4 till the instant color of the solution start changing to yellow we stop the stop watch and record the time5- Repeat the procedure at least three times and calculate the average.6- Tabulate the results in record B.b-Experimental procedure to measure the time necessary for 10 % solvolysis of t butyl chloride (0.1 M concentration) in 70 % water 30% acetone solvent at a temperature greater than room temperature by ten degrees.B, b, I-1- Prepare 500 ml of 0.1 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it 1.2- Prepare 100 ml of 0.1 M N aOH solutions (in water) and put it in an Erlenmeyer flask and label it 2.3- Using a burette take 30 ml of the solution in Erlenmeyer flask 1 and put it in an Erlenmeyer flask and label it 3.4- By a graduated pipette put 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it 4.5- Using a graduated cylinder measure 67 ml of distilled water added to Erlenmeyer flask 4.7- Add two drops of bromo-phenol blue indicator to flask 4.B, b, II-1- Suspend the flasks 3 and 4 in a water bath full with ice and water, allowing the temperature of the flasks and their contents to equilibrate for ten minutes.(to reach the temperature of the water bath)2- Adding quickly the solution in flask 4 to solution in flask 3 and start the stop watch to count for time in seconds.3- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into flask 4 to minimize the errors in the results.4- The color of the mixed solutions is blue, so continue swirling the solution in flask 4 till the instant color of the solution start changing to yellow we stop the stopwatch and record the time5- Repeat the procedure at least three times and calculate the average.6- Tabulate the results in record B.Record A poke out numberTemperatureTime of 10 % reactionAverage time / secondsRecord BRun numberTemperatureTime required for 10% reactionAverage time/secondsAverage time/ secondsReferences* E. Brady, James. E. Humiston, Gerard., General Chemistry Principles and Structure, second edition, SI version, john Willy and sons, Inc.* Brewester, Vaderwerf and McEwen. Unitized Experiments in positive Chemistry, 3rd Ed.* Streitwieser, Andrew. H. Heathcock, Clayton. Introduction to Organic Chemistry.* H. Reusch, William. An Introduction to Organic Chemistry.* J. Laidler, Keith. Chemical kinetics. 2nd ed.* Search engines that where usedo www.google.como www.yahoo.com* Goldwhite, Harold. R. Spielman, John. College Chemistry, 1984