Study&Guide&for&Exam&II,&CHM2211L9Fall2011&!Introduction!This!document!will!provide!you!with!a!list!of!questions!on!which!to!base!your!study!for!Exam!II.!Do!not!consider!these!questions!as!a!template!for!the!type!of!questions!that!will!be!asked!on!the!exam.!Use!them!as!a!basis!to!determine!the!type!of!information!that!yo u!sh o uld !ha ve!in!o rde r!to!write !the!ex am !su cces sfu lly.!You!are!also!provided!with!the!answers!to!some!of!the!questions!from!the!post@labs.!The!mechan ism@rela ted !qu e stio n s!w ill!be !d iscu s sed!during!the!review!session!on!Monday,!7th!November.!In&general,!you!shou ld!know !the!follow ing!for!all!experiments: !• Molecular!structures!of!all!the!reagents!used!• Nomenclature!and!Lewis!structures!of!the!reagents!• Mechanisms!of!reactions!• Principles!behind!the!techniques!used!in!the!experiment!You!should!also!memorize!the!IR!and!NMR!frequencies!listed!in!your!lab!manual,!and!the!NMR!spectra!from!the!list!provided!to!your!by!Dr.!Profeta.!! !Experiment&1:&Physical&Properties&of&Organic &Solve nts&1. What!are!the!different!types!of!intermolecular!forces!that!can!operate!in!chemical!compounds?!Ion$Ion,&Ion$Dipole,&Dipole$Dipole,&Dispersion,&H$Bond&2. Which!intermolecular!forces!operate!in!polar!compounds?!Which!intermolecular!forces !op era te!in !no n@polar!compounds?!Polar:&Ion$Dipole,&Dipole$Dipole,&Dispersion,&H & B o n d&Non$Polar:&Dispersion,&&3. Which!physical!properties!can!be!used!to!gauge!the!po larity!o f!a!compound?!Higher&boiling&point&because&of&stronger&intermolecular&forces,&melting&point,&and&solubility.&4. What!is!the!origin!of!polarity?!How!can!you!determine!the!polarity!of!a!compound!from!its!molecular!structure?!One&side&is&more&electronegative&than&the&opposing&side.&&If&a&compound&is&not&symmetrical,&then&it&is&probably&not&as&polar.&&5. What!is!the!most!common!example!of!a!polar!solvent?!Water&6. Which!solvents!would!you!use!to!dissolve!the!following!solutes:!• Solutes:!NaCl,!Aspirin,!Caffeine,!Benzoic!Acid!• Solvents:!Water,!Acetone,!Dichloromethane!7. Arrange!the!following!compounds!in!increasing!order!of!polarity:!!!!!!!!! !!!! !!! !!&Answers&to&Selected&Post9Lab&Questions:&1. Why!does!ethyl!acetate!have!a!higher!boiling!point!than!hexanes,!even!though!they!are!appro xim ate ly!the!sa m e!m ole cula r!weig ht?!The&ester&functional&group&in&EtOAc&makes&it&slightly&polar,&which&increases&the&extent&of&the&intermolecular&dipole$ dipole&interactions.&2. Why!does!methanol!have!a!lower!boiling!point!than!ethanol,!even!though!it!is!more!polar?!!Besides&polarity,&the&other&factor&which&affects&intermolecular&forces&(and&thus&the&boiling&point,&melting&point&etc.)&is&the&molecu lar&weig ht.&M ethan ol&has&a&lower&molecular&weight&and&this&contributes&to&its&lower&boiling&point.&!Experiment&2:&Recrystallization,&Solubility,&and&Melting&Points&1. What!is!the!basic!principle!on!which!recrystallization!works?!Purify&a&solid&by&dissolving&it&in&a&solvent&that&is&soluble&at&a&high&temperature&and&insoluble&at&a&lower&tempera ture.&&&2. How!would!you!determine!that!a!solvent!is!suitable!to!recrystallize!a!particular!solute?!It&must&be&soluble&at&a&high&temperature&and&insoluble&at&a&lower&temperature.&&!3. Why!is!it!better!to!use!an!Erlenmeyer!flask!for!recrystallization,!as!compared!to!a!beaker?!So&that&the&vapors&do&not&escape&and&so&that&they&recondense&down&into&the&solution.&&4. What!is!the!purpose!of!boiling!chips!or!a!stir!bar!during!recrystallization?!To&prevent&bumping&and&even&heating.&&&5. What!are!some!ways!to!maximize!the!yield!of!a!recrystallization!procedure?!Cool&down&product&as&slow&as&possible.&&&Answers&to&Selected&Post9Lab&Questions:&1. Why!must!you!allow!recrystallized!samples!to!dry!completely!before!determining!the!m.p.?Solvent&will&disturb&the&crystal&packing&of&the&solid,&thus&the&m.p.&will&be&lower&than&a&pure &com po und .&&2. What!is!the!purpose!in!knowing!the!literature!solubility!data!when!doing!a!recrystallization?&&To&get&a&rough&idea&how&much&solvent&to&add&for&a&certain&amount&of&solid&and&to&get&an&idea&how&much&of&the&crystals&will&stay&in&solution&upon&cooling.&&3. Why!is!acetanilide!soluble!in!water,!while!trans@cinnamic!acid!is!not?&Because&it&has&a&higher&ratio&of&polar&surface&area&to&total&surface&area.&& &Experiment&3:&Principles&of&Chemical&Extraction&1. What!is!the!basic!principle!on!which!chemical!extraction!works?!Separate&two&compounds&using&two&solvents&that&are&immiscible.&(Two&different&compounds&in&two&different&solvents.)&2. Which!chemical!reaction!can!you!use!to!solubilize!a!carboxylic!acid!in!water?!Give!an!example!with!a!chemical!reaction.!React&the&carboxylic&acid&with&a&base&so&that&it&becomes&a&salt&and&then&it&is&soluble&in&water.&&R$COOH&+&NaOH&$>&R$C$OO($)&+&Na(+)&3. Which!chemical!reaction!can!you!use!to!solubilize!an!amine!in!water?!Give!an!example!with!a!chemical!reaction.!R$NH2&+&HCL&&$>&R$NH3(+)&+&Cl($)&4. Draw!a!flowchart!to!describe!how!you!will!separate!a!mixture!of!cellulose,!benzoic!acid!and!aminoethane.!Q&from&test&1&Cellulose&with&diethyl&ether&and&filter&it&out&$>&add&HCL&to&make&aqueous&layer(salt,&R$NH3(+),&Cl($))&separate&from&Benzoic&acid&$>&add&NaOH&to&layer&$>&&5. Can!water!and!acetone!be!used!as!solvents!for!a!chemical!extraction!procedure?!Justify!your!answer.!No,&because&they&are&miscible..&&6. What!is!the!purpose!of!venting!during!the!separation!procedure?!To&release&pressure&from&vapors.&&&Answers&to&Selected&Post9Lab&Questions:&1. Given!a!mixture!of!caffeine!and!benzoic!acid,!what!would!happen!if!they!were!added!to!a!separatory!funnel!with!CH2Cl2!and!1M!HCl?!Which!compound!go!into!which!layer!and!why?&The$caffeine$has$one$N$atom$(N09)$that$will$add$protons$in$acid$and$thus$the$caffeine$will$become$charged$and$go$into$the$aqueous$layer.&! !Experiment&4:&Nucleophilic&Substitution&Reaction&Kinetics&!&Answers&to&Selected&Post9Lab&Questions:&1. What!will!be!the!primary!side!reaction(s)!that!are!also!taking!p lace ?!Is!th is!affecting!your!kinetic!data?!The&E1&rxn&will&compete&with&the&SN1.&This&rxn&should&not&alter&the&k&values&because&HX&will&be&produced&in&this&rxn&as&well&as&the&SN1&rxn.&&& &Experiment&5:&Thin&Layer&Chromatography&of&Analgesics&1. Which!is!the!stationary!phase!in!the!TLC!you!did?!Which!was!the!mobile!phase?!The&stationary&phase&is&the&plate&and&the&mobile&phase&is&the&solvent.&&2.