ORG SYN & ANALYSIS IV
ORG SYN & ANALYSIS IV CHEM 234
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Date Created: 10/21/15
The DielsAlder Reaction Atom Economy Josh Levin Toms Aamp39ML1139VcrsigDcpartmcnt of Chemistry College Sm 1011 TX 778423012 e Vzhc34gmai com April 9 2010 ABSTRACT H30 0 OCH3 O CH quotTr V 3 O 0 Yield 8796 This experiment s objective was to successfully carry out the DielsAlder reaction a cycloaddition reaction between a conjugated diene and a dienophile to obtain an aromatic compound with retained stereochemistry The reaction between the conjugated diene transtrans24 decadienal and the dienophile diethyl fumarate was carried out and based off of spectroscopic data the predicted product 4pentane56diethyl cyclohexanoatecyclohexeZene benzoic acid was obtained in 88 yield however there were several impurities in the sample Introduction Green Chemistry is a vast range of ideas to reduce waste reducing harm to the environment reduce health and fire hazards and many other idealistic notions The Diels Alder reaction exemplifies the ideals of the concept of llGreen Chemistry in that the Diels Alder reaction epitomizes excellent atom economy uses little to no reagents there are very few if any byproducts of the reaction and the reacted products are generally not toxic to the environment or human health these are 4 of the 12 principles of Green Chemistry1n this 1 Introduction to Organic Laboratory Techniques A Small Scale Approach 2quotd ed Pavia Lampman Kriz paper we describe the DielsAlder reaction between the conjugate diene trans trans2 4 decadienal and the dienophile diethyl fumarate to produce 4pentane5 6diethyl cyclohexanoatecyclohexeZene benzoic acid The DielsAlder is a very exothermic reaction due to the fact that the products are always more stable than the reactants due to the stability of the resulting aromatic ring In this case simply mixing the reactants and applying heat generally allows the reaction to go to completion With this in mind the reactants were placed in a round bottom flask along with a magnetic stir bar over a heating mantle As the reaction proceeded along with a general constant level of heating around 200 C the reaction was monitored by TLC with the reaction mixture in comparison to pure diethyl fumarate and trans trans2 4decadienal This was to assess the disappearance diethyl fumarate due to the fact that diethyl fumarate was the limiting reagent and the conjugated diene would always be present in excess As the reaction proceeded over time and using 90 hexanes10 ethyl acetate as a solvent it was ascertained that the diethyl fumarate lane in the reaction mixture began to gradually disappear indicating the reaction had indeed been carried out to the extent that there was little to no diethyl fumarate present in the reaction mixture This conclusion was supported by the lack of peaks of diethyl fumarate save for one in a 1H NMR and the presence of product peaks Results and Discussion and Engel Thompson BrooksCole Belmont California 2005 pg 255 Structure of Product H30 0 OCH3 O CH 3 o O H The Aldehyde and ether peaks are valuable indicators in proton NMR determination with peaks for the Aldehyde in the 97106 range and the ether peaks in the 33456 range These peaks are both present in the 1H NMR of the product The pentane group attached to the cyclohexene ring is also another area of interest simply due to the number of carbons these are all present in the 13C NMR taken as well as the aldehyde and ester carbons However in both the 1H NMR and 13C NMR there is the presence of ethyl acetate and nhexane impurities due both being used as the solvent to purify the reaction mixture Also in the proton NMR there was a small peak at 68 5 indicating the presence of diethyl fumarate which means that not all of diethyl fumarate was consumed in the reaction there were also peaks in the 26 26 6 region that indicate the presence of residual conjugated diene which also mean that not all ofthe conjugated diene reacted to produce product Because recrystallization was not an option to purify the product after the reaction the method of column chromatography was used to purify the product using 90 hexanes and 10 ethyl acetate as the solvent Although using the method of TLC is vital to determining the progress of the reaction each TLC run is taking away from the reaction mixture and thus reducing the yield of the product of the reaction The percent yield of the reaction can be raised by either reducing the number of TLC tests or using an alternative method to monitor the reaction progress that does not take product from the reaction mixture Percent yield mol product obtained mol limiting reagent 100 4pentane5 6diethyl cyclohexanoate cyclohexe2ene benzoic acid 324 gmol Amount of product obtained 057 g 057g 1mol324g 00017592593 mol product Diethyl fumarate limiting reagent 0002 mol 000175925930002 08796 08796 100 8796 Product NMR data 1H NMR CDCI3 9456 s 2H 94 6 s 1H 745 6 t 1H 72 6 d 1H 715 6 d 1H 48 6 m 1H 42 6 q 2H 405 6 q 2H 18 6 m 2H 165 6 m 2H 150 6 m 2H 10 6 m 2 H 090 6 t 3H 130 NMR CDCI3 d 216 207 133 61 36 31 26 22 19 11 Estimable product based of NMR spectra product peak heights vs impurity peaks 40 Crude 1H NMR spectra 1H NMR CDCI3 945 6 d 70 6 t 686 6 s 55 6 m 428 6 m 32 6 m 26 6 m 20 6 m 12 6 m 08 6 t The crude proton NMR spectra details that the diethyl fumarate is still present but some to most of it has reacted the conjugated diene trans trans 2 4 decadienal is still present in large amounts but the product has begun to form indicated by the aldehyde peaks in the 96 6 range Experimental 1 Assemble reaction apparatus attach a round bottom flask to a reflux condenser over a heating mantle Add sand to the heating mantle and attach a thermometer to a clamp and place the thermometer bulb in the sand to read the temperature of the sand bath Attach a nitrogen line to the top ofthe reflux condenser Lquot Obtain 045 mL of conjugated diene trans trans 2 4 decadienal and place in round bottom flask To this add 038 mL of diethyl fumarate 3 Add magnetic stir bar to round bottom flask attach round bottom flask to reflux condenser start condenser begin heating and stirring 3 Bring temperature to 200 C begin monitoring reaction by TLC every 20 minutes Take 5 TLC s overall When reaction has reached 200 C after 20 minutes of constant heating back off heat until temperature is 125 C 5 Take proton NMR of reaction if reaction has gone to completion test for possibility of purification by recrystallization 21 If recrystallization not possible begin column chromatography using 90 hexanes10 ethyl acetate as solvent 7 Monitor eluates by TLC and discern which eluate contains pure product 339 Group product and place into rotary evaporator to drive off solvent Obtain 1H NMR and 13c NMR spectra 3 New percentage yield 08796 40 3518 FriedelCrafts Acylation Josh Levin T oXas AampMDopartmont ofCIomllgtry College Sta tion TX 778423 012 ovino34gma11 com April 22 2010 ABSTRAC General reaction scheme H30 CH3 Cl 0 CIAl CI H3c ll CI gt H30 The FriedelCrafts Acylation of 1566 mL of pcymene with resulted in the formation of 385mL of 39139 p H39 397 CH3 Cl HCI CH3 Cl Al Cl 10 mL of acetyl chloride under 18g ofAIuminum Chloride catalyst E l1 p p was obtained in an overall 2326 yield with possible isomers also being formed Introduction Aromatic compounds are a separate class of compounds that are unique in chemistry forthey demonstrate their own particular characteristics with respect to reactivity stability and chemical properties1Aromatics are extremely important to organic chemistry due to their reactivity that allows them to act as both nucleophiles and electrophiles their incredible stability and most importantly the various reactions they undergo and the ability for certain reaction to achieve carboncarbon 1 Organic Chemistry 7M edition Mcmurw John Cengage learning Mason Ohio 2008 bonds The reaction between pcymene and Acetyl chloride under an Aluminum chloride catalyst is better known as a Friedel Crafts Acylation reaction after Charles Friedel and James Crafts who discovered theses carbon carbon bond forming reactions in 1877 Z This paper will describe the FriedelCrafts acylation of pcymene the results based off NMR and IR spectroscopy show that the product ofthe reaction is 5isopropyI2 methylacetophenone This is to be the expected major product of the two possible products due to the effects of steric hindrance preventing the addition of the acetyl group closer to the isopropyl group 2 quotFriedelCraftsReactionquot Mchale Marw httpcnxorgcontentm15260latest October 16 2007 Results and Discussion The reaction occurred within a 500mL 3 necked round bottom flask with a Calcium chloride trap the aromatic p cymene was slowly added to the acetyl chloride and aluminum chloride solution via separatoryfunnel with dichloromethane solvent to help alleviate the overproduction of heat After a suitable amount of reaction time the product was isolated from the organic layer and washed with anhydrous sodium sulfate to get rid of any residual water The solvent Dichloromethane was then driven off via vacuum distillation and the product was reisolated in a clean round bottom flask 1H NMR crude product 1H NMR coca 755 s 1H 708 5 d 1H 706 5 d 1H 530 5 s 2H 29 5 m 1H 26 5 s 3H 25 5 s 3H 205 5 s 3H 122 5 d 3H 120 5 d 3H The major material obtained was 5isopropyl2 methylacetophenone the IR spectroscopic data indicates a medium absorption at 90858 cm391 and 88971 cm 1 and a strong absorption at 82643 cm391 that corresponds to a l 2 4 substituted aromatic compound3 The key dictating data that determines that 5isopropyl2methylacetophenone was formed deals with the anisotropy of electron withdrawing groups Because of the acetyl group an electron withdrawing group the ortho and para protons would be expected to show a 3 2 ratio of downfield to upfield when compared to the Meta proton the 1H NMR of both the crude product and the pure product show this ratio with respect to the proper protons4 1H NMR pure product 1H NMR coca 755 s 1H 708 5 d 1H 706 5 d 1H 29 5 m 1H 26 5 s 3H 25 5 s 3H 205 5 s 3H 122 5 d 3H120 5 d 3H 3 r 39 1 39 Laboratory T hninrl A ltmnH lt n Approach pg 897 2quotd ed Pavia Lampman Kriz 4 Introduction to Organic Laboratory Techniques A Small Scale Approach pg 935 2 ed Pavia Lampman Kr39z 13c NMR CDCI3 d 202 147 138 135132 130 128 34 30 24 21 IR Major peaks 296074 cm391 medium absorption indicates alkyl sp3 peak which is probably due to isopropyl and methyl groups Strong absorption at 1700 cm391 indicative of carbonyl peak Medium absorption at 90858 cm391 and 88971 cm391 and a strong absorption at 82643 cm391 that corresponds to a l 2 4 substituted aromatic compound PCymene contains an isopropyl group and a para substituted methyl group on an aromatic benzene ring Upon alkylation with acetyl chloride there are only two possible isomeric products 5isopropyl2 39 39 39 andll thyl2p pm yl cyclohexyl ethanone However the formation of l 5methyl2propan2yl cyclohexyl ethanone is very sterically hindered due to the close proximity of the isopropyl group The acylation will favor the formation of5isopropyl2methyacetophenone due to the less steric hindrance of the methyl group on the acetyl group that is adding to the ring However it must be noted that there are usually steric effectshindrances upon the third substitution of an aromatic ring in general To determine the percentage purity the 1H NMR spectral data of the pure product was used There is a multiplet at 295 that is close to an impure absorption at 345 that is either due to isomeric product or residual pcymene 356 2825 xlOO 356 2825x X126 100 X percentage purity Percentage purity 874 Percentage yield grams obtained of product theoretical yield of product Limiting reagent in reaction was pcymene in which 01 moles were used gt maximum yield of product 01 moles 01 moles 1762Sgl mole 17625 g 41 g amount of product obtained 17625 02326 02326 100 2326 percent yield 12 Lquot UJ 33 Ln 9 Experimental Set up apparatus obtain a 500 mL 3necked round bottom flask place a stopper in one neck a reflux condenser into the second neck with a Calcium chloride trap inserted into the top of the reflux condenser and a separatory funnel also fitted with a Calcium Chloride trap into the final neck Place the 500 mL round bottom flask into a ice bath Obtain 18g of Aluminum Chloride and mix with 33 mL of dichloromethane place in 500 mL round bottom flask Obtain 18g of acetyl chloride mix with 20 mL of dichloromethane add this mixture to separatory funnel Proceed to add contents of separatory funnel to round bottom flask Obtain 01mol of aromatic compound mix with 13 mL ofdichloromethane After addition of acetyl chloride mix place aromatic compound mix into separatory funnel and add to 500 mL round bottom flask slowly After addition of aromatic compound mix remove ice water bath allow to stand at room temperature for 30 minutes while stirring the flask with a magnetic stir bar Add contents of 500 mL round bottom flask to a 500 mL beaker containing 66g of ice and 33 mL of HCl Stir with a glass rod 33 O Add this mixture to a 250 mL Separatory funnel and extract the organic layer and save it Extract the aqueous layer with 30 mL of dichloromethane and add this extract to the organic layer saved earlier Wash these combined organic layers with 666 mL of sodium bicarbonate solution Dry solution with approximately 35 g of anhydrous sodium sulfate for 1015 minutes Perform Vacuum distillation based upon boiling point of expected product 5 isopropyI2methylacetophenone 90 C soate product in round bottom flask and perform IR and NMR spectroscopy to determine identity of product Density Functional Theory Studies of Cyclobutane Acetamide and 1Aminoethenol Josh Levin T 5X35 AampM UniversityDepatbnent ofClzemIlstr College Sta tron TX 77842 ew39zze34gmazl com April 26 2010 ABSTRACT O i HO H N KCH D H2N CH3 2 2 The calculations for these structures were full optimizations using a B3LYP method and a 631G basis set39 Cyclobutane was found to have an optimal energy at 157101724 hartries Acetamide was found to have an optimal energy at 207 138561 hartries and laminoethenol was found to have an optimal energy at 193040393 hartries Introduction The DFT calculations performed in this experiment are based upon indirectly applying quantum mechanics by focusing on the distribution of the electron density of the structure and assigning functionals for the distribution and second order functions for the energy The ability to perform these calculations have several key important consequences these calculations serve to help chemists understand the favorable arrangement of compounds the transition states of molecules undergoing certain reactions as well as providing key data that allows chemists to calculate enthalpy entropy and heats of formation for various compounds Out of all the structures cyclobutane was found to be the least stable in energy Acetamide keto form was found to be more stable than its enol form laminoethenol In this paper DFT calculations predict that cyclobutane to have an optimal energy of l57l hartries Acetamide to have an optimal energy of 2071 hartries and laminoethenol to have an optimal energy of l93 hartries Results and Discussion The various structures provided were analyzed by a computer using the B3LYP method and 63lG basis to do a DP T calculation for each separate molecule these calculations determined the optimal energy for the compound in its most stable arrangement Part A A The relative energy of transZbutene is 985932 kcalmol the relative energy of lbutene is 985892 kcalmol and the relative energy of cis2butene is 989403 kcalmol B trans2butene is 398 kcalmol more stable than 1butene C cis2butene is 3471 kcalmol more stable than trans2butene39 this energy difference can be accounted to a difference in the strain energy D The energy values listed in McMurry on pg187 vary vastly from the calculated energies the difference in energy between cis2butene and trans 2butene is 1 kcalmol but the calculated difference is 3471 kcalmol 1 E McMurry lists the strain energy for cyclobutane as 264 kcalmol39 the difference in energy between trans2butene and cyclobutane from the calculated figures is 105 kcalmol therefore the listed and calculated figures do not match This is probably due to the method and basis sets used for the McMurry calculation are not the same as the ones used for this experiment it is also possible that the McMurry calculations were Ab who or Semi empirical calculations rather than DFT which can lead to differences in energy values Part B A For the propan2one to prop1en2ol ketoenol equilibria the enthalpy of reaction was AH 003 kcalmol For the acetaldehyde to ethanol ketoenol equilibria the enthalpy of reaction was AH 051 kcalmol For the acetic acid to ethene1 1diol keto enol equilibria the enthalpy of reaction was AH 7518 kcalmol For the Acetamide to 1 aminoethenol ketoenol equilibria the enthalpy of reaction was AH 005 kcalmol Km eA39AGRT39 assuming AGAH gt Km eA39AHRT AH converted to cal from kcal and T is assumed room temperature of 20 C For the propan2one to prop1en2ol ketoenol equilibriagt Km 2718A 301 987293 15 Km 095 For the acetaldehyde to ethanol ketoenol equilibriagt Km 2718A 510198729315 Km 042 For the acetic acid to ethene1 1diol ketoenol equilibriagt 1 Organic Chemistry 7M edition Mcmurry John Cengage learning Mason Ohio 2008 Kai 2718A 75180198729315 Keq11110A56 For the Acetamide to 1aminoethenol ketoenol equilibriagt Km 2718A 50198729315 0 92 eq C Based off the DFT calculations acetic acid is the least stable keto form with an optimal energy at 153774298 Hartries and the most stable keto form is Acetamide with an optimal energy of 20914 Hartries In order of increasing keto stability for the compounds analyzed is as follows acetic acid acetaldehyde propan2one Acetamide D Propa2one when converted to its enol tautomer has the ability to place the double bond between the carbonyl carbon and either of its alpha carbons when undergoing bromination of a carbonyl compound the mechanism dictates that the double bond acts as the nucleophile to attack the bromine atom Therefore the fact that there are two alpha carbons to which a double bond could be formed increases the chancesrate at which the bromination occurs and thus this carbonyl compound will be brominated most easily Acetic acid contains an electron withdrawing alcohol on the other side of the alpha carbon the oxygen of the alcohol group withdraws electron density from the double bond in ethenel 1diol and thus makes the double bonded alpha carbon less able to act as a nucleophile This results in acetic acid the least able to undergo the process of bromination E Propan 2one is the most stable of the keto forms thus it is the least reactive towards nucleophiles Acetic acid is the least stable of the keto forms thus it is the most reactive towards nucleophiles Part C For this experiment the DFT calculations using a B3LYP method and 631G basis set was employed to find the optimal energies for cyclobutane Acetamide and 1aminoethenol Cyclobutane was found to have an optimal energy at 157101724 hartries Acetamide was found to have an optimal energy at 207138561 hartries and 1aminoethenol was found to have an optimal energy at 193040393 hartries The importance of this experiment in respect to cyclobutane is that in comparison to the listed values for McMurry the calculated values are significantly different showing either error in the calculations performed and the possibility of a different method and basis set used The importance in respect to Acetamide and 1aminoethenol shows that the accepted mechanisms for ketoenol tautomer halogenations and alpha carbonyl nucleophilic substitution have fundamental evidence in respect to stabilization energies The more likely a ketoenol tautomer is to halogenations in effect is due inpart to how stable in energy that compound is Conclusion Part D The goal of this study was to perform DFT calculations using a B3LYP method with a 631G basis set to calculate various isomers of butenes cyclobutane and various ketoenol tautom ers Trans2 butene was found to have optimal energy of 157118 hartries 1butene was found to have an optimal energy of 157112 hartries cis2butene was found to have an optimal energy of 15767 hartries and cyclobutane was found to have an optimal energy of 157101 hartries PropanZone was found to have an optimal energy of 19307 hartries acetaldehyde was found to have an optimal energy at 1537742998 hartries acetic acid was found to have an optimal energy at 153774298 hartries and Acetamide was found to have optimal energy at 209138561 Prop1 en2ol was found to have an optimum energy at 19304 hartries ethenol was found to have an optimum energy at 15326 hartries ethene1 1diol was found to have an optimum energy at 22897 hartries and 1aminoethenol was found to have an optimum energy at 20908 hartries
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