Question

2) Predict the order of reactivity (1=least, 4=most) of primary, secondary, tertiary, and aryl halides toward nucleophilic displacement by an SN1 reaction mechanism. Explain

3) Give a detailed summary of the chemistry in both reactions SN2 and SN1 in details please for both reactions. include any general statements about the experiments.

LAB)o Organic Chemistry I Lab CHEM 3512 Nueleophilic Substitution Reactions: Sl vs S2 To review Sul, S2, El and E2 reactions and mechanisms and compare and contrast the effect of the leaving group and the structure of the substrate on nucleophilic substitution reactions of 1°, 2, 3° alkyl halides and aryl halides Student will work in pairs, but each student will turn in his/her report for grade. Chemicals and Solvents, Chemical Abstract Service [CAS]: (1) 1-chlorobutane, [109-69-3] (3) 2-chlorobutane, [78-864 (5) bromobenzene, [108-86-1) (2) 1-bromobutane, [109-65-9 (4) 2-bromobutane, [75-26-3] des 1. Ss2 Reaction. nt you will study the reaction of several haloalkanes with sodium iodide, under SN2 reaction conditions. reaction to be performed, the nucleophile is I, and is introduced into the solution as sodium iodide dissolved in e. If the reaction occurs, sodium bromide or sodium chloride will form and precipitate in acetone. aceton The general reaction is: Lor Procedure a. Write the reactions (total of 5) for each of the primary aryl substrates listed above with in ple the table on the following page. b. Obtain 5 clean, dry, new test tubes (10 x 75 mm size) and parafilm. Devise a scheme to enable you to keep track of each tube, reaction time, observations, etc. You are working in pairs so you can keep track of many activities simultancoushy If you don't have a good scheme, you will lose track of what you are doing and have to begin again. Place six (6) drops of starting material halide, delivered by the disposable pasteur pipet, into the correctly labeled test c. tube and immediately "stopper" with a square of parafilm. d. To the test tube containing the alkyl halide, add 1.0 mL of the sodium iodide in acetone solution with a disposable plastic pipet and record the exact time of addition in the table in 2.a. Swirl the test tube to ensure complete mixing, and observe the test tube for the formation of a precipitate (which may appear only as cloudiness in the solution, ie, turbidity). Record how long it takes for a precipitate to appear, some reactions occur quickly while others take considerable time. After 5 minutes at room temperature, if no precipitate (cloudiness or turbidity) forms, place the test tube in the S0 C water bath and heat for another 10 minutes while noting the time at which any precipitate occurs. Do not let the reaction run longer than a total of 15 minutes. Record all your observations in the table e. Repeat the procedure for the remaining halides. Have your instructor review your results before you analyze the data. f. Dispose of all chemicals from the test tubes into the liquid organic waste bottle, rinse the test tubes with a small squeeze of acetone, add the rinse to the waste bottle, and throw the test tubes into the broken glass containers. Page I of 6

Answer 1

SN' - Reaction rightarrow SN' stand for Nueleophilic Substitution Unimolecular because Rate determine step is unimolecular. Thus rate depend only on alk_4 holida not on N4- SN' Reaction takes place in 3 - steps 1 rightarrow Formation of carbonation (more stable) 2 rightarrow Nucleophilic attack 3 rightarrow Depretonation Rbs Depend on carbecation FOrmation so more stable acrbocation will participate in SN' Reaction Stability of Carbocation [3 degree > 2 degree > 1 degree > 0 degree] 3 degree - carbocation will be more stable because it stabilized by + Inductive effect of cH_3 \r\n # 1 CH_3 - CH_2 CH_2 - CH_2 - Cl I - chlorebutane least stable carbocation will form 1 degree - carbocation so it will be least reactive. # 4 rightarrow 2 - bromobutane rightarrow 2 degree - carbocation will be more stable than 1 degree - carbocation so it will be more reactive. Reactivity order of halide rightarrow [I > B > u > F] \r\n 1 degree - carbocation will be least stable than