Thaum tau txais ntau hom alkylbenzenes thiab acylbenzenes hauv kev lag luam, Friedel-Crafts cov tshuaj tiv thaiv tau dhau los. Nws yog ib qho ntawm ob txoj hauv kev paub txog kev sib txuas ntawm cov khoom sib txuas, thiab nws cov kev txwv tsis raug tswj kom ua tiav cov txiaj ntsig siab dua ntawm cov khoom.
Ntau txog cov txheej txheem arene alkylation
Cov piv txwv nto moo tshaj plaws ntawm Friedel-Crafts cov tshuaj tiv thaiv yog kev sib cuam tshuam ntawm methyl chloride (CH 3 Cl) nrog benzene (C 6 H 6) nyob rau hauv lub xub ntiag ntawm txhuas chloride (AlCl3), qhov twg cov zis yog toluene (C7 H9). Cov tshuaj tiv thaiv no tau txais hauv xyoo 1877 los ntawm ob tus kws tshawb fawb - Charles Friedel thiab James Crafts. Tom qab ntawd nws tau dhau los ua ib qho tseem ceeb rau kev tsim khoom ntawm alkylarenes.
Lub ntsiab synthesis yog kev sib cuam tshuam ntawm benzene thiab nws homologues nrog ib qho alkyl halides nyob rau hauv lub xub ntiag ntawm lub thiaj li hu ua Lewis acids. Lub ntsiab ntawm qhov kev hloov ntawm reagents tsis hloov: cov tshuaj tiv thaiv ib txwm ua raws li tib txoj cai. Derivatives ntawm noTxoj kev yog tsim cov alkylbenzenes hauv cov organic chemistry los ntawm kev sib cuam tshuam ntawm cawv thiab inorganic acid, carbonium ion thiab ib lub nplhaib aromatic.
Txoj kev thib ob yog kev hloov pauv ntawm cov saw hlau ntawm ntau yam muaj ntxhiab ketones nyob rau hauv muaj zinc amalgam (ZnHg) nrog hydrochloric acid (HCl) lossis hydrazine (N 2 H 2 ) nrog lub hauv paus muaj zog. Ob qhov kev tshwm sim yog qhov txo qis: thawj yog hu ua Clemmens cov tshuaj tiv thaiv, qhov thib ob yog hu ua Kizhner-Wolf tshuaj tiv thaiv.
Tsis tas li, yog tias muaj cov nyiaj tsis txaus ntseeg nyob rau hauv cov saw hlau sab, lawv tuaj yeem raug txo los ntawm cov tshuaj tiv thaiv ntawm nickel catalyst (Ni) nyob rau hauv muaj cov roj hydrogen (H2).
Reaction mechanisms
Cov ntaub ntawv piav qhia txog ob txoj hauv kev ntawm cov tshuaj tiv thaiv, thiab ob qho tib si ua raws li kev hloov pauv ntawm electrophilic. Qhov txawv tsuas yog nyob rau hauv qhov xwm ntawm lub electrophile: thawj rooj plaub, qhov no yog ib tug alkyl carbonium ion (lwm lub npe yog carbocation), uas yog tsim los ntawm kev sib ntxiv ntawm ib tug halogen ion rau ib tug Lewis acid raws li tus pub. -acceptor hauv paus ntsiab lus, thiab nyob rau hauv cov ntaub ntawv thib ob, nws yog ib-theem creation ntawm ib tug sab hauv complex ntawm tag nrho cov koom reagents raws li tib txoj kev. Txhua qhov kev xaiv tau piav qhia hauv qab no.
Reaction los tsim cov carbonium ion
Cov txheej txheem no cuam tshuam txog kev sib txuas ntawm 3 theem, qhov twg Lewis acids, piv txwv li AlCl3, TiCl4, SnCl 4, FeCl3, BF3, HF ua raws li txheej txheem catalyst.
rauXav txog qhov Friedel-Crafts cov tshuaj tiv thaiv, kev sib cuam tshuam ntawm benzene thiab 1-fluoropropane (C 3 H 6F) nyob rau hauv muaj boron trifluoride BF. raug xaiv 3 ua tus catalyst.
Nyob hauv thawj kauj ruam ntawm tus txheej txheem, C3H6‒F cuam tshuam nrog BF3, ntxiv halogen ion raws li txoj cai pub dawb. Nyob rau sab nraud lub zog, boron muaj ib lub xov tooj dawb (acceptor), uas yog nyob ntawm fluorine nrog ib khub tsis sib koom ntawm electrons (tus pub). Vim qhov sib ntxiv no, cov pa roj carbon atom C, sawv ntawm ib sab ntawm halogen F hauv 1-fluoropropane, tau txais tus nqi zoo thiab dhau los ua cov tshuaj propyl carbonium ion heev. Cov cuab yeej ntawm cov ions no nce nyob rau hauv cov koob thawj → theem nrab → tertiary, yog li ntawd, nyob ntawm cov xwm txheej hauv cov khoom ntawm cov tshuaj tiv thaiv alkylation, cov saw hlau sab yuav rov ua dua mus rau txoj haujlwm zoo dua.
Ntxiv mus, qhov tshwm sim carbocation reacts nrog benzene thiab koom nrog ntawm qhov chaw sib cog lus ntawm carbon thiab hydrogen atoms, hloov electron ceev mus rau C ntawm lub nplhaib aromatic.
Nyob rau theem thib peb, qhov tshwm sim ntawm qhov tshwm sim nrog ib qho ionized Lewis acid, qhov twg H atom yog sib cais tawm ntawm lub arene thiab koom nrog cov detached F nrog tsim ntawm hydrogen fluoride HF, thiab cov tshuaj tiv thaiv cov khoom ua n- propylbenzene, isopropylbenzene thiab txo BF3.
Synthesis tsim ib qho chaw sab hauv
Cov tshuaj tiv thaiv mechanism suav nrog kev tsim cov txheej txheem nruab nrab, qhov twg hauv ib theem ntawm pawg alkyltxav los ntawm halogen mus rau lub nplhaib uas muaj ntxhiab, thiab lub halogen mus rau Lewis acid, tsim ib khub ion uas decomposes rau hauv ib qho alkylbenzene, ib qho ntxhia compound, thiab txo cov catalyst.
Nyob ntawm cov tshuaj tiv thaiv derivative
Cov Friedel-Crafts cov tshuaj tiv thaiv rau benzene thiab nws cov homologues nrog cawv nyob rau hauv muaj cov ntxhia acids ua raws li tib lub tswv yim. Hauv qhov no, hydrogen atom txuas mus rau hydroxide ion thiab, tawg tawm, tsim cov dej molecule. Qhov tshwm sim carbonium ion yog txuas rau cov pa roj carbon monoxide nyob rau hauv lub nplhaib uas muaj ntxhiab ntawm qhov chaw ntawm nws daim ntawv cog lus nrog H. Cov atom no raug cais tawm, ntxiv rau cov kua qaub residue, thiab vim li ntawd, alkylbenzene yog synthesized.
Nyob rau hauv unsaturated hydrocarbons, detached hydrogen nce nyob rau hauv qhov chaw ntawm ob daim ntawv cog lus, tsim tib carbocation txuam nrog cov acid residue. Hydrogenation ntawm alkene tshwm sim nyob ze cov pa roj carbon atom uas tsim cov qauv zoo tshaj plaws. Tom qab ntawd qhov kev tshwm sim tshwm sim zoo li hauv rooj plaub dhau los.
Ib qho ntawm cov khoom sib txuas ntawm cov khoom sib txuas kuj yog Friedel-Crafts acylation cov tshuaj tiv thaiv, qhov twg cov kua qaub chlorides (RCOCl) siv los hloov cov alkyl halides los tsim cov ketones aromatic.
Ntxiv ob lossis ntau dua alkyl residues
Benzene hauv Friedel-Crafts cov tshuaj tiv thaiv tuaj yeem ntxiv los ntawm 2 mus rau 6 tus neeg hloov pauv. Nws yuav tsum raug sau tseg tias txhua zaus kev sib cuam tshuam sai dua, txij li daim ntawv cog lus hauv lub nplhaib aromatic tsis muaj zog nyob rau thawj zaug.synthesis. Cov txheej txheem ntawm kev tsim ntawm polyalkylbenzenes tuaj yeem ua tiav nyob rau hauv chav kawm ntawm ib qho tshuaj tiv thaiv, yog li ntawd, ntau tshaj ntawm cov tshuaj tsw qab yog siv los tswj cov khoom ntawm cov khoom xav tau. Siv cov qauv no, koj tuaj yeem maj mam qhia ib pawg ntawm ib lub sijhawm rau hauv cov qauv ntawm benzene thiab nws homologues.
Hauv Friedel-Crafts cov tshuaj tiv thaiv, toluene tau yooj yim ntxiv rau pawg alkyl tom ntej, txij li lub arene twb tau ua haujlwm nrog kev hwm rau kev hloov pauv electrophilic. Hauv cov khoom siv tshuaj tiv thaiv ntawm 0 ° C yuav muaj qhov sib npaug ntawm ortho- thiab para-xylene, thiab thaum kub nce mus txog 80 ° C, feem ntau tsuas yog cov meta-compound yuav ua ke. Qhov no tau piav qhia, raws li tau piav qhia hauv qab no, los ntawm cov txiaj ntsig ntawm lub zog ntawm kev tsim ntawm qee txoj haujlwm nyob ntawm qhov cua sov ntawm qhov sib tov.
Kev txuas ntxiv ntawm qhov kev sib txuas no yog lub peev xwm ntawm polyhaloalkanes los txuas ntau tshaj ib lub nplhaib uas muaj ntxhiab ntawm lub ntsiab mechanism.
Synthesis nta
Nyob rau hauv cov organic chemistry, kev tsim ntawm kev sib xyaw ntawm alkylbenzene isomers tau piav qhia los ntawm ob qho laj thawj. Ua ntej, raws li tau hais los saum toj no, kev tsim cov carbocation qee zaum cuam tshuam nrog kev kho kom zoo dua qub, vim muaj ntau yam khoom tsim. Qhov thib ob, lawv cov khoom muaj pes tsawg leeg yog tswj hwm los ntawm kev tswj hwm qhov kub thiab txias (los ntawm 0 ° C mus rau 80 ° C), uas yog, nrog rau qhov kub thiab txias kom them nyiaj rau kev siv hluav taws xob ntawm kev tsim cov qauv tshwj xeeb, ib qho tuaj yeem ua tiav.siab dua tawm los ntawm ib qho ntawm isomers. Tib lub hauv paus ntsiab lus siv rau kev tsim cov dialkylbenzenes, qhov twg ortho- thiab para-txoj hauj lwm muab txoj hauv kev rau cov meta-orientations nrog nce kub.
Kev txwv ntawm kev siv cov khoom sib txuas
Muaj 3 nuances vim yog Friedel-Crafts cov tshuaj tiv thaiv tuaj yeem mus nrog cov kev mob tshwm sim lossis tsis mus txhua.
Taw qhia ntawm cov khoom siv hluav taws xob tsis zoo rau hauv lub nplhaib uas muaj ntxhiab yog nrog los ntawm arene deactivation nrog rau kev hloov pauv ntxiv. Yog li, piv txwv li, thaum nitronium ion ntxiv rau alkylbenzenes, qhov kev sib txuas yog qhov nyuaj dua, vim tias nws rub cov electron ceev ntawm nws tus kheej vim qhov nyiam ntawm nitrogen los sau ib qho khoob ntawm lub zog sab nraud. Rau tib lub laj thawj, polynitration lossis, piv txwv li, polysulfonation tshwm sim nyob rau hauv cov xwm txheej hnyav heev, txij li nrog rau txhua qhov kev sib txuas tom qab lub nplhaib aromatic poob nws cov reactivity.
Yog li ntawd, Friedel-Crafts synthesis tsis ua haujlwm yog tias lub nplhaib uas muaj ntxhiab muaj cov khoom siv hluav taws xob, tshwj xeeb tshaj yog cov khoom muaj zog uas khi Lewis acids (piv txwv li -NH 2, -NHR, -NR2). Tab sis cov tshuaj tiv thaiv, piv txwv li, nrog halobenzenes lossis aromatic carboxylic acids ua raws li cov txheej txheem raug, txawm hais tias lawv tsis tshua muaj zog.
Ib qho tseem ceeb tseem ceeb kuj yog qhov kev hloov pauv ntawm cov carbonium ion hauv cov txheej txheem lossis cov khoom kawg, vim tias nws tau cuam tshuam los ntawm cov txheej txheem synthesis, tshwj xeeb, qhov kub thiab txias ntau dhau ntawm cov khoom alkylated.
Sivalkyl halides R‒X (R=alkyl pab pawg, X=halogen) Ar‒X halogenides (Ar=aromatic compound) tsis tuaj yeem siv, vim lawv nyuaj heev los tshem tawm ib qho kev hloov pauv txawm nyob rau hauv lub zog ntawm Lewis acids.
