October 29 - o‘Cec'twm air: 29/ (9E1; 2:7, 2008 Addition...

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Unformatted text preview: o‘Cec'twm air: 29/ (9E1; 2:7, 2008 Addition reactions: 0 ifs-1.6 No‘fiz'iilits c. 13.. does NOT nitwa MEWMCWE. We've seen that the way to make an alkene is through an elimination reaction on an appropriate MW of substrate, like an alkyl halide: Marc-am w " 63 WW). —~———a—\—.z: «a» OH (5 e H H 23%., /¢'—- ‘ I The opposite of the elimination process to form an alkene is an addition reaction, where the elements of a smail molecule are added across the double bond: Alger—CH2 + H26 _—~+ fiscal—42x ;4H<o ‘Bfteouécmg,oc WW8< H‘x hijfimamg, C—H&C—?Ca/3-WL5 This is because the n: electrons of the double bond are nucleophilic when in the presence of a sufficiently strong electrophiie, and this can result in a process called electrophm'c addition. m E A 4‘ ere-’5: ma ? H69 If your alkene starting material is symmetrical, t ere is only one possible product. ft» 32:. If your alkene starting material is asymmetricai (not symmetrical), more than one product can result in an addition reaction. Consider the additEon reaction of HBr across this alkene: H30 H HBr H3O CH3 There are two possibilities for product formation: H30>=<H H3!” HHH flaw of “30 CH3 :5!» 4:662);qu H30 _ H H355, H H3O CH3 3 E M ngvmkot, ,WMW,WWWWW.D , . . .. . .. . .. . . m. _ ‘ .Regioselectivity in electrophilic addition reactions Regioselectivity: The electrophilic addition reaction of HX to an aikene is regl‘oselective because one constitutional isomer is formed preferentially. (Remember that selectivity always reflects a difference in reaction ra es. This reaction follows Markovnikov‘s mic and gives the Markovnikov product. Markovnikov's rule: “H69 iw't’l‘zz mange/Mime: G-OLOLLDL “ta—'fi’fie. fess ma;th claim (Ma/Km «t‘xvt/ H) m6 GLOWL/W(ffiam}wjrffia We. 6%fargfa. achWWcM/Leabdm) - H {Np H76 £6 acoLatcaL'fio— cmflméfipfie W¢M%)W% Mme/“MC %0 We. H c Jets Me‘fimm H) Mechanism of Markovnikov addition of HX c an alkene: m .. W H -- e.) )4 + -r: mes. Mt ‘ .332» 2- {B/Lo-Ww_ 2m5%/Wm Seismic}? for—mat m e. ~3W' 3- WWW Wt imOo‘E'Oeab 2°amfio—cmw ' 11.54 4 9.213.644. ofw'xS-tl. 0... v act/H a 09 H Jumow :;>5\ 0: MMéoVnc‘éo v “Didi—fan X K amt. Mmkowkofl 051;; MMOVW'ko'O [3] Ct; own/"CU— Mama/zoo amfix— “Loaféu/ @MQo/ves q. a’Ekwe. “u 0H (Eyck-2: Wm M) «mimwwwm x2: “2,39% x ,, ,, MIROO'VVC £013 8g \ Hz . . ' - - 5 O n r “MI-b. {'LO'W 85” I amt-dew! Regioselectivity in addition reactions: Anti-Markovnikov addition The other possible product is caited the anti-Markovnikov product. To obtain this product, we must use different conditions. The reaction foEEows a completely different mechanism. o‘" HBr B _ New» H V >_ H' fess wg’sfifwfeoi, 6953/6 «3:19 ROOR /& e .OLL 0333’ v9 a}; J)“ ROOR is a functional group called a peroxide. The 0-0 bond is the weakest bond in the system, k!» try so when We apply energy, it breaks in an initiation step: A” . 9' Mechanism: FAEE—Mowe MEG W kgnlf'tclau'tL-M 5 (1) KNOLL/3.— R 3%.). 2 weak {69/10 a.ka Who/e, «EC-taker. :7 )3 (2) J—I a, w, abshamow: ———-———m—}— R‘OH +5 ‘jfp: .. W Mbéfiwfimt W co>é< wélv: ——-+ “M” II o Bjé. @& flan“ H 3MLWLWSM ) (2) + “‘3‘?“ "i’ It is great to have choices! Examples of synthetic applications: H 32:. 14:51, 311, Newt3 “3 ———————>- -—————~——>— RooR. 3MP 3° Mtge Mole. \ H34, H H “2.0 /—\ “a” fl *’*" %\ SOMEj/GW imzmwflmmmw “muhmimsmvhpw . “MMAMWMWM ,,i .., i W W October 29, 2008 ConcepTests (1) Addition of HCl to 3-methyl-1-pentene gives TWO products. One of these is 2-chloro-3-methylpentane. Identify the other product. (A) 1-Chloro-3-methylpentane (B) 3-Chloro-3-methy1pentane (C) 3-Chloro-2-methy1pentane (D) 2-Chloro~2-methy1pentane Correct Answer: B (2) Consider this reaction from a mechanistic point of View: /CH2CH3 \CHZCHZCH3 HCl What is the relationship between the products formed in this reaction? (A) Constitutional Isomers (B) Diastereomers (C) Enantiomers (D) Meso form (hence, identical) Correct Answer: C ...
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October 29 - o‘Cec'twm air: 29/ (9E1; 2:7, 2008 Addition...

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