Thursday, May 23, 2019

Chemistry Extended Essay Essay

To investigate the consequence of 2-bromo-2-methyl propane concentration and temperature of the system on the pose of reception of solvolysis of 2-bromo-2-methyl propane in 90% ethyl alcoholDone by Habib Is locoweeddar HinnFriends Boys SchoolJune 22, 2007To investigate the pitch of 2-bromo-2-methyl propane concentration and temperature of the system on the rate of chemical chemical reaction of solvolysis of 2-bromo-2-methyl propane in 90% ethyl alcoholIntroductionThe major intersection of the solvolysis of t -butyl chloride in 70 % wet 30 % acetone is t-butyl alcohol, with a subtle amount of isobutylene being formed as a by productAnd this is with accordance of first order kinetic and suggests a two step weapon in which the rate ascertain step consists of the ionization of t-butyl chloride, and in this mechanism a carbonium ion is formed as inter- mediate and this link ups immediately to near by nucleophile (in this cuticle nucleophile is a neutral molecule) the initial p roduct is t-butyl carbonium ion.Note1 if the nucleophile is neutral the product will be charged since the leaving group takes both bonding electrons away with itSo chemists have proposed to general types of mechanism1- Nucleophilic electric switch Sn1The ionization step in a Sn1 reaction is endothermic and much slower 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 equation 4, and as a result, the overall rate of reaction is not abnormal by smorgasbords in the concentration or kinds of nucleophilic reagents present.Note2 the factor which determines the mechanisms employed is typically the nature of the substrate it self and not the particular nucleophileNote3 if the sum of the energy of the product is lower than the energy of the reactant the reaction is exothermic, and if the product have mettlesomeer energy than the reactant the reaction is endothermic.2- Eliminatio n 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 solvent is t-butyl alcohol.(Note4 electrophile an electron deficient atom, ion or molecule that as affinity for an electron pair, and will 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 only reactant that is undergoing 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 second step, so their relative molar concentrations rather than their nucleiophilities are t he primary product determining factor, and by using nucleophilic solvent 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 orient them-selves in such a way as to decrease the electrostatic forces surrounded by 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 atomic derive 1 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 total reaction, the over all 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 dissolving agent)The relaxation 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 issue 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 food colour when the NaOH has been neutralized, and clocking of the reaction should begin at the instant.So according to kinetic stridements footstep of reaction = K t butyl chlorideWhere K is the particular proposition rate constant in S -1 and t butyl chloride is the concentra tion 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 condemnation 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 logarithm Rcl 0 = KtRcl t2.303 enter 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 calculate K1- since the equationKt = 2.303 Log Rcl 0Rcl tIs an equation of a straight line (y=mx+b) with slope k. and intercept =0, a plot of 2.303 log 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 Rcl 0Kt = 2.303 Log Rcl 0 = 2.303 log (1.11)0.90 Rcl 0And there fore,K = 0.104TSo by determination the value of K and compensate it in the rate of reaction equation Rate = KRcl where the concentration of Rcl is known we can calculate 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 resolving.The effect of temperature on the solvolysis of t -butyl chloride in 70%water 30%acetone solvent.In nearly every instance an annex in temperature causes an increase in the rate of reaction, because the total fraction of all of the t butyl chloride 1molecules having energies equal to or greater than activation energy (Ea)Corresponds to the shaded portion of the area under the draw in increases by increasing the temperature and by comparing the area for two different temperature, we see that the total fraction of t- butyl chloride molecules with sufficient kinetic energy to undergo reaction increases with increasing temperature and consequently, so does the reaction rate.Note7 c hanging the concentration affects the rate of reaction changing the temperature affects the rate constant as well as the rate.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 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 victorious 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 characteristic of the reactionWe can calculate the rate const ant 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 solution.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.ProcedurePart A the effect of concentration on the rate of solvolysis of t butyl chloride in 70%water 30%acetone solvent.a-E xperimental procedure to measure the time incumbent for 10 % solvolysis of t butyl chloride (0.1 M concentration) in 70 % water 30% acetone solvent at room temperature.A, a, I-1- Prepare viosterol ml of 0.1 M t- butyl chloride in acetone only and put it in an Erlenmeyer flaskful and chase it 1.2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer and label it 2.3- apply a burette take 30 ml of the solution in flask 1 and put it in another Erlenmeyer and label it 3.4- By a receive pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it 4.5- development a calibrated cylinder measure 67 ml of distilled water added to an Erlenmeyer flask 4.6- chip in two drops of Bromo-phenol blue indicator to flask 4.A, a, II-1- Add quickly the solution in Erlenmeyer flask 4 to solution in flask 3 and bestir oneself the develop watch to count for time in seconds.2- Swirl the assortment and after one or two seconds immediately pour the co mbined solutions adventure into Erlenmeyer flask 4 to minimize the errors in the results.3- The color of the mixed 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 interpret the time.4- Repeat the procedure at least three times and calculate the average.5- Tabulate the results in record A.b-Experimental procedure to measure the time unavoidable 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- utilise 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 quickly 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 potpourri 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 mixed 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 butyl chloride in 70%water 30%acetone solvent.a-Experimental procedure to measure the time necessary for 1 0 % solvolysis of t butyl chloride (0.1 M concentration) in 70 % water 30% acetone solvent at zero 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- set aside the Erlenmeyer flasks in a water bathroom full with ice and water, allowing the temperature of the Erlenmeyer flasks and their contents to equilibrate for ten minutes.2- Adding quickly the solution in Erlenmeyer flask 4 to solution in Erlenmeyer flask 3 and sta rt 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 NaOH solutions (in water) and put it in an Erlenmeyer flask and label it 2.3- Using a burette take 30 ml o f 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 reco rd the time5- Repeat the procedure at least three times and calculate the average.6- Tabulate the results in record B.Record ARun 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 thorough 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

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