Carbocation vs Carbanion
Qhov sib txawv tseem ceeb ntawm carbocation thiab carboanion yog lawv cov nqi; lawv yog ob hom organic molecular nrog cov nqi sib txawv. Carbocation yog qhov zoo them ion thiab carboanion tsis zoo them ion. Lawv qhov kev ruaj ntseg nyob ntawm ntau yam, thiab qee qhov ntawm lawv tseem ceeb heev hauv kev sib txuas ntawm lwm cov tshuaj lom neeg.
Carbocation yog dab tsi
A carbocation yog ib hom tshuaj uas nqa cov nqi zoo ntawm cov pa roj carbon atom. Nws lub npe muab lub tswv yim meej tias nws yog cation (ib qho zoo ion), thiab lo lus carbo hais txog carbon atom. Carbocation suav nrog ntau pawg; thawj carbocation, theem nrab carbocation, thiab tertiary carbocation. Lawv raug cais raws li tus naj npawb ntawm cov pab pawg alkyl txuas nrog cov pa roj carbon atom zoo. Lawv qhov ruaj khov thiab qhov rov ua haujlwm sib txawv nyob ntawm cov khoom siv no.
Carbocation Stability Trend
Carbanion yog dab tsi
A carboanion yog hom organic molecular uas muaj hluav taws xob tsis zoo nyob ntawm cov pa roj carbon atom. Nyob rau hauv lwm yam lus, nws yog ib tug anion nyob rau hauv uas ib tug carbon atom muaj ib tug unshared khub ntawm electrons nrog peb substituents. Nws tag nrho cov valence electrons yog sib npaug rau yim. Lawv raug tsim los ntawm kev tshem tawm cov pab pawg zoo lossis cov atoms los ntawm qhov nruab nrab molecule. Lawv yog ib qho tseem ceeb heev li tshuaj intermediates los ua ke lwm yam khoom xws li yas thiab polyethene (los yog polyethylene). Qhov tsawg tshaj plaws carbanoin yog 'methide ion' (CH3–); tsim los ntawm methane (CH4) los ntawm kev poob ntawm proton (H–).
Qhov txawv ntawm Carbocation thiab Carbanion yog dab tsi?
yam ntxwv ntawm Carbocation thiab Carbanion
Carbocation: Carbocation yog sp2 hybridized, thiab qhov tsis muaj p-orbital lies perpendicular rau lub dav hlau ntawm peb pawg hloov. Yog li ntawd, nws muaj ib tug trigonal planar molecular qauv. Carbocation yuav tsum muaj ib khub electron kom tiav octet. Lawv tuaj yeem hnov mob nrog nucleophiles, tuaj yeem deprotonated los ntawm pi-bond thiab tuaj yeem rov kho dua hauv tib hom.
Carbanion: Ib qho alkyl carboanion muaj peb txoj hlua khi thiab ib khub ib leeg; yog li nws hybridization yog sp 3, thiab geometry yog pyramidal. Lub geometry ntawm allyl los yog benzyl carboanion yog planar, thiab cov hybridization yog sp 2Lub octet tiav nyob rau hauv lub sab nrauv orbit ntawm ib tug carboanionic carbon atom thiab nws coj raws li ib tug nucleophile rau react nrog electrophiles.
Kev ruaj ntseg:
Carbocation: Carbocation stability nyob ntawm ntau yam. Nws ruaj khov dua thaum ntau pawg -R txuas nrog cov pa roj carbon zoo. Yog li, tertiary carbocation yog qhov sib piv ruaj khov dua li cov thawj.
Cov qauv Resonance kuj nce kev ruaj ntseg.
Carbanion: Kev ruaj ntseg ntawm carboanion nyob ntawm ntau yam; Electronegativity ntawm carbanionic carbon, resonance nyhuv, inductive nyhuv tshwm sim los ntawm txuas ntxiv hloov thiab stabilization los ntawm >C=O, -NO2 thiab CN pawg muaj nyob rau carbanionic carbon
Definition:
Induct effect: Nws tuaj yeem ua qhov kev soj ntsuam pom cov txiaj ntsig ntawm kev sib kis ntawm tus nqi los ntawm cov saw hlau ntawm atoms hauv cov molecule, uas ua rau muaj qhov dipole mus tas li hauv daim ntawv cog lus.
Piv txwv ntawm Carbocation thiab Carbanion
Carbocation:
Primary Carbocation:
Nyob rau hauv thawj (1°) carbocation, cov pa roj carbon atom zoo yog txuas rau tsuas yog ib pawg alkyl thiab ob lub hydrogen atoms.
Secondary Carbocation:
Hauv qhov thib ob (2°) carbocation, cov pa roj carbon atom uas muaj txiaj ntsig zoo txuas rau ob pawg alkyl (uas tej zaum yuav zoo ib yam lossis txawv) thiab ib qho atom hydrogen.
Tertiary Carbocation:
Nyob rau hauv tertiary (3°) carbocation, cov pa roj carbon zoo yog txuas rau peb pawg alkyl (uas tej zaum yuav yog ib qho kev sib xyaw ua ke los yog sib txawv), tab sis tsis muaj hydrogen atoms.
Carbanion:
Carboanion kuj tau muab faib ua peb pawg tib yam li hauv carbocation; thawj carboanion, theem nrab carboanion, thiab tertiary carboanion. Qhov ntawd kuj ua tiav raws li tus naj npawb ntawm –R pawg txuas nrog anionic carbon atom.
