Qhov sib txawv tseem ceeb ntawm thawj thiab theem nrab allylic carbocations yog tias thawj allylic carbocation tsis ruaj khov dua li theem nrab allylic carbocation.
Ib qho allylic carbocation yog ib qho resonance stabilized carbon qauv. Nws yog ib qho ion uas muaj tus nqi zoo. Hauv cov ions no, qhov zoo ion yog muab tso rau ntawm allylic carbon atom (ib qho allylic carbon atom yog cov atom uas nyob ib sab mus rau ob daim ntawv cog lus). Thawj allylic carbocation yog ib qho allylic carbocation qhov twg tus nqi zoo yog muab tso rau ntawm thawj carbon atom thaum theem nrab allylic carbocation yog ib qho allylic carbocation qhov twg tus nqi zoo yog muab tso rau ntawm cov pa roj carbon thib ob.
Primary Allylic Carbocations yog dab tsi?
Primary allylic carbocation yog ib qho allylic carbocation qhov twg tus nqi zoo yog muab tso rau ntawm thawj carbon atom. Nws yog lub npe hu ua carbocation vim nws muaj cov nqi zoo ntawm cov pa roj carbon atom. Feem ntau, ib qho allylic carbocation nqa tus nqi zoo +1. Ib tug thawj carbon atom yog ib tug carbon atom uas txuas rau ob hydrogen atoms thiab ob daim ntawv cog lus. Feem ntau, ib qho nruab nrab carbon atom tsim plaub daim ntawv cog lus, thiab ib daim ntawv cog lus raug tshem tawm thaum nws tsim cov cation. Thawj cov pa roj carbon atom tsuas muaj ib pawg aryl lossis alkyl txuas rau nws thaum lwm daim ntawv cog lus yog C-H daim ntawv cog lus.
Daim duab 01: Allylic Resonance
Feem ntau, cov molecule uas muaj ob daim ntawv cog lus ntawm carbon atoms tuaj yeem muaj cov qauv resonance ruaj khov. Resonance txhais tau hais tias electrons nyob rau hauv lub pi daim ntawv cog lus ntawm ob daim ntawv cog lus yog muab faib thoob plaws hauv lub molecule raws li ib tug delocalized system qhov twg stability yog nce ntau tshaj nyob rau hauv ib txwm molecule. Yog li ntawd, yog hais tias peb yuav mus rau lub npe ib tug compound raws li ib tug thawj allylic carbocation, lub compound yuav tsum muaj ib tug zoo nqi ntawm allylic carbon atoms nyob rau hauv tag nrho cov ua tau resonance qauv ntawm cov molecule.
Dab tsi yog Secondary Allylic Carbocations?
Secondary allylic carbocation yog ib qho allylic carbocation qhov twg cov nqi zoo yog muab tso rau ntawm cov pa roj carbon thib ob. Nws yog lub npe hu ua carbocation vim nws muaj cov nqi zoo ntawm cov pa roj carbon atom. Feem ntau, ib qho allylic carbocation nqa tus nqi zoo +1. Qhov thib ob carbon atom yog cov pa roj carbon atom uas txuas rau ib lub atom hydrogen, ob daim ntawv cog lus thiab ib pawg alkyl lossis aryl. Feem ntau, ib qho nruab nrab carbon atom tsim plaub covalent bonds qhov twg ib daim ntawv cog lus raug tshem tawm thaum nws tsim ib qho cation. Ib qho carbon atom thib ob muaj ob pawg aryl lossis alkyl txuas rau nws thaum lwm daim ntawv cog lus yog C-H daim ntawv cog lus.
Qee lub sij hawm, lub sij hawm thib ob allylic carbocation yog siv thaum tsuas yog ib qho qauv resonance ntawm ib qho chaw tshwj xeeb muaj cov nqi zoo ntawm cov pa roj carbon thib ob. Qhov tseem ceeb tshaj, qhov thib ob allylic carbocations ruaj khov dua li cov thawj allylic carbocations vim tias lawv muaj ob pawg aryl lossis alkyl txuas nrog cov pa roj carbon atom uas coj tus nqi zoo (aryl lossis alkyl pawg yog pawg electron rho tawm yog li, lawv tuaj yeem txo tus nqi zoo ntawm cov khoom siv hluav taws xob. carbon atom).
Qhov txawv ntawm Thawj thiab Thib Ob Qhov Allylic Carbocations yog dab tsi?
Allylic carbocations yog cov qauv tshuaj uas tus nqi zoo nyob rau ntawm allylic carbon atom ntawm cov molecule. Lub allylic carbon atom yog cov pa roj carbon atom uas nyob ib sab ntawm ob daim ntawv cog lus. Thawj allylic carbocation yog ib qho allylic carbocation qhov twg tus nqi zoo yog muab tso rau ntawm thawj carbon atom thaum theem nrab allylic carbocation yog ib qho allylic carbocation qhov twg tus nqi zoo yog muab tso rau ntawm cov pa roj carbon thib ob. Qhov sib txawv tseem ceeb ntawm thawj thiab theem nrab allylic carbocations yog tias thawj allylic carbocation tsis ruaj khov dua qhov thib ob allylic carbocation.
Cov ntawv qhia hauv qab no qhia txog qhov sib txawv ntawm thawj thiab theem nrab allylic carbocations.
Summary – Thawj vs Secondary Allylic Carbocations
Allylic carbocations yog cov qauv tshuaj uas tus nqi zoo nyob rau ntawm allylic carbon atom ntawm cov molecule. Lub allylic carbon atom yog cov pa roj carbon atom uas nyob ib sab ntawm ob daim ntawv cog lus. Qhov sib txawv tseem ceeb ntawm thawj thiab theem nrab allylic carbocations yog tias thawj allylic carbocation tsis ruaj khov dua qhov thib ob allylic carbocation.
