Organic Chemistry Laboratory
Organic Chemistry Laboratory CHE 276
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This 5 page Class Notes was uploaded by Dr. Alana Bauch on Wednesday October 21, 2015. The Class Notes belongs to CHE 276 at Syracuse University taught by Nancy Totah in Fall. Since its upload, it has received 37 views. For similar materials see /class/225657/che-276-syracuse-university in Chemistry at Syracuse University.
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Date Created: 10/21/15
CHE 276 There Will be no lecture on October 29th Lecture Will resume the following week Synthesis of an Alkyne from an Alkene 0 Th 3 week 3 synthes s step 1 t N 13969 Brse gt acetic acid step 2 triethylene glycol heat 0 Overa convers on a kene to a kyne d fficu t to ach eve n a 3 ng e step Experiment 8 Synthesis of an Alkyne from an Alkene Part A Synthes s of mesost bene d brom de Part B Synthes s of d pheny acety ene Read ng Wade Ch 8 pgs 321 324 342345 Ch 9 pgs 393394 Step1 Bromination of Stilbene N IllaD Br3e gt acetic acid e ectroph 0 add t on of brom ne to a doub e bond genera react on of a kenes 0 occurs rap d y and wth defined stereochem stry N H Br3e 0 typ ca y done wth brom ne Br2 corros ve qu d h t ea 0 We w use pyr d n um hydrobrom de perbrom de aka pyr d n um tr brom de orange so d l Brz conven ent source of Br2 generated in situ 36gt Br 9 Step 1 Reaction Mechanism E ectroph 0 Add t on 0 N G 39 Br3e gt acetic acid heat 0 Reacton s stereospecfic se ect ve add t on across doub e bond re at ve or entat on of groups on doub 9 bond carbons stays the same backs de attack of brom de 8N2 mechan sm Reaction Mechanism E2 e m naton 0Q triethylene glycol 160170 C T Hgo Br39 0 p 62 Br H2O rH Br gt H4 H 39 Br39 Br 0 0 dehydroha ogenat on s concerted bond break ng and bond format on occur at the same t me Step 2 Dehydrobromination W O 0 gt triethylene glycol 160170 C e m nat on of Br n the presence of a strong base genera react on of organ 0 ha des a so has spec fic stereochem ca requ rements can be used to form both a kynes doub e e m nat on or a kenes In TWO Weeks November 3 November 6 Experiment 8 Synthesis of an Alkyne from an Alkene A Synthes s of mesod bromost bene brom nat on of a doub 9 bond B Synthes s of d pheny acety ene dehydrobrom nat on doub e e m nat on of brom ne DUE DehydrationGC Lab Report exp 7 Lab Reports are due at the beginning of your regular lab session Experimental Details 39 Step 1 Bromination 1 Comb ne reactants h an Erenmeyer flask d sso ve Est bene n acet c ac d heat gent y ISO35 C add pyr d n um hydrobrom de perbrom de pyr d n um tr brom de rnse vesse wa s wth a tte acet c ac d f necessary 2 Swr to m x amp contnue heat ng 5 m n crysta s product w separate 9 Coo react on vesse n co d water 4 Co ect product by vacuum fi trat on 0quot Wash crysta s spar ng y w th ce co d methano dry crysta s shou d be co or ess dry thorough y under vacuum us ng your s de arm test tube 03 We gh product w use to ca cu ate the ye d N Save a sma amount for TLC note th s product s the start ng mater a for the next react on 8 We w not take an IR Experimental Details 39 Step 2 Dehydrobromination 4 Coo react on m xture to room temp s ow y add co d water add water dropw se wh e st rrng so ut on wth the be ng st ck KBr 5 water so ube so at d phenyacety ene w separate 5 Co ect product by vacuum fi trat on rnse wth a sma amount of ce co 01 water dry as best you can save a sma samp e for met ng po nt 6 Recrysta ze product from hot ethano th nk about the techn que before you arr ve use a m n mum amount of hot so vent coo s ow y to room temperature then n ce co ect crysta s by vacuum fi trat on dry through y 7 Ana yze products LC both procucts styrene me t ng po nt of both crude amp recrysta zed d pheny acety ene we w not be tak ng IRs n th s exper ment Experimental Details Step 2 Dehydrobromination 1 Comb ne reactants n a arge tared test tube N use 059 of mater a obta ned n ste remember to keep a sma tc samp e CAUTION KO s corros ve avo c 3quot hand 5 w In care add a bo ng st ck eat n a hot pre heated sand bath 185190 C for 5 m nutes so at KBr w se arate use a thermometer to mon tor temperature of the sand bath P ease mon tor Dont et t get too hot 3 Eva uate react on progress by TLC spot both the start ng mater a saved from step 1 amp react on m xture react on comp ste 7 move on to step 39 react on ncomp ate hear 5 In n more check agan Q ow do you know fthe react on s done ook for the d sappearance of styrene start ng mater a 00k for the appearance of a new spot product cons der that you a so have other reagents n the test tube Calculating Percent Yield 1 Wrte a ba anced chem ca equat on use to determ ne mo ar rat 0 of start n9 mater a s to products 2 Ident fy the mtng reagent need to know amount of mater a 5 used need mo ecu ar we ghts of start ng mater a s amp products a cata yst 3 never the m tng reagent 3 Determ ne the theoret ca y e d the max mum amount of product you cou d poss b y recover 4 Ca cu ate ye d amount of product obta ned g o ye d theoret ca y e d 9 X100 Calculating Percent Yield Example 1 Wrte a ba anced chem ca equat on MC Nal M 1 4 NaCl amount 0 539 219 0 729 MW 92 57 9lmo 149 89 9mol 184 O2 9mol 58 44 9mol 2 Ident fy the mtng reagent make a Tab e of Reagents as wou 01 go n Append x A I reagents 1 amount 1 moles 1 equivalents I l 1 chlorobutane 1 O 539 1 5 72 1 l limiting reagent 1 Na 1 2 19 1 14 o 1 2 4 ca CU ate mo es Of reactants example calculating moles of 1 chlorobutane 1 mole RCI 92 579 RCI determ ne equ va ents of reactants dent fy m tng reagent a cata yst w never be the rn t ng reagent 0 539 RCI X 5 72 mol RCI Calculating Percent Yield Example I React on 01 4 Nal amen 1 1 Wrte a ba anced chem ca equat on M01 4 N21 gtace quote 4 NaCl amount M o 539 219 o 729 2 92 57 gllnol 149 89 9lmo 184 02 9rnol 58 44 glinol Calculating Percent Yield Example acetone 01 Nal 4 NaCl amount 0 539 219 O 729 MW 92 57 9llno 149 89 9lmo 184 02 9llno 58 44 9lmo limitin9 rea9ent 3 Determ ne the theoret ca ye d 1 mole ROI 1 mole R 184 02 9 R 0539 ROI X 92579 RCI x 1 mole RCI x 1 moleR 1 59 RI 4 Ca cu ate ye d amount of product obtained 9 o erld x 100 theoretical erId 9 0729 obtained X100 69 1 059 theory Lab Practical October 27 October so I Format You w be asked to accomp sh spec fic aboraty tasks wth n a g ven t me frame a tasks w nvo ve techn ques you have done before e ng TLC recrysta zat on extract on d st at on co umn chromatography I The Lab Pract ca w be he d dur ng your regu ar y schedu ed ab per od there 5 no makeup for the Lab Pract ca Be sure you are there I Show up on t me f you are ate you w not get addtona tme I The Lab Pract ca s c osed book no outs de mater a s of any k nd are a owed no ca cu ators or ce phones are a owed just you a penc and organ c chem stry come prepared Lab Practical October 27 October so I Preparat on Rev ew proceduresamp techn ques from ear er abs exp 15 top cs may no ude metng po nt TLC recrysta zat on extract on d st at on co umn chromatography Be sure you understand the concepts beh nd these techn ques You may have to use th s know edge to make dec s ons about what to do I The Good News no pre ab wr te up s requ red there 5 no ab report requ red for the pract ca Exper ment 7 ab report dehydrat on amp GC s not due unt the 9 week November 3 As a ways t w be due at the beg nn ng of your regu ar ab sess on
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