Qhov sib txawv tseem ceeb ntawm LiAlH4 thiab NaBH4 yog tias LiAlH4 tuaj yeem txo cov esters, amides thiab carboxylic acids whereas NaBH4 tsis tuaj yeem txo lawv.
Ob leeg LiAlH4 thiab NaBH4 yog txo tus neeg sawv cev. Tab sis LiAlH4 yog ib qho kev txo qis heev dua li NaBH4 vim tias Al-H daim ntawv cog lus hauv LiAlH4 tsis muaj zog dua li B-H daim ntawv cog lus hauv NaBH4. Qhov no ua rau Al-H daim ntawv cog lus tsis ruaj khov. Yog vim li cas rau qhov no yog qhov tsawg electronegativity ntawm Aluminium piv rau Boron. Yog li ntawd, qhov tsawg electronegativity hloov cov electron ceev ntawm hydrogen nyob rau hauv Al-H tshaj li ntawm B-H daim ntawv cog lus. Raws li qhov tshwm sim, LiAlH4 yog qhov zoo dua hydride pub.
LiAlH4 yog dab tsi?
LiAlH4 yog lithium aluminium hydride, uas yog tus neeg sawv cev muaj zog. Cov kws tshawb fawb Finholt, Bond thiab Schlesinger thawj zaug nrhiav pom qhov sib xyaw no hauv xyoo 1947. Tsis tas li ntawd, muaj ntau yam kev siv ntawm cov tshuaj no hauv cov txheej txheem organic synthesis. Nws yog qhov txaus ntshai reactive ntawm dej, uas ua rau tso tawm gaseous hydrogen (H2).
Daim duab 01: Txo lub zog ntawm LiAlH4
Nws zoo nkaus li cov muaju dawb hauv daim ntawv ntshiab. Tab sis qib kev lag luam LiAlH4 yog cov hmoov xim grey vim muaj kev sib kis. Cov khoom sib xyaw no yog hygroscopic heev thiab tsis muaj ntxhiab tsw. Cov molar loj yog 37.95 g / mol, thiab lub melting point yog 150 ◦C. Yuav kom ntxuav cov khoom no, peb tuaj yeem siv txoj kev recrystallisation nrog diethyl ether.
NaBH4 yog dab tsi?
NaBH4 yog sodium borohydride, uas yog tus neeg sawv cev txo qis. Tsis zoo li LiAlH4, qhov no yog ib qho tsis muaj zog txo tus neeg sawv cev. Nws zoo nkaus li dawb crystals uas yog hygroscopic heev. Ntxiv mus, cov compound no yog soluble hauv dej thiab kuj reacts nrog dej. Txawm li cas los xij, nws maj mam hydrolyzes hauv dej.
Daim duab 02: Cov qauv ntawm Sodium Borohydride
Cov molar loj ntawm cov tshuaj no yog 37.83 g / mol, thiab qhov melting point yog 400◦C. Thaum kub siab dua, nws zoo li decompose. NABH4 hmoov feem ntau nyiam ua pob. Txhawm rau ua kom huv qhov sib xyaw no, peb tuaj yeem siv cov txheej txheem recrystallisation nrog cov diglyme sov. Txawm hais tias qhov sib xyaw no decomposes hauv nruab nrab lossis acidic nruab nrab, nws ruaj khov ntawm pH 14. Cov tebchaw uas NaBH4 tuaj yeem txo tau suav nrog cov organic carbonyls xws li aldehydes thiab ketones, acyl chlorides, thiol esters, imines, thiab lwm yam.
Qhov txawv ntawm LiAlH4 thiab NaBH4 yog dab tsi?
LiAlH4 yog lithium aluminium hydride uas yog tus neeg sawv cev muaj zog. Nws qhov hnyav yog 37.95 g / mol. Nws yog ib qho muaj zog txo tus neeg sawv cev thaum piv rau NaBH4 vim qhov sib xyaw no tuaj yeem txo cov esters, amides thiab carboxylic acids. Qhov no yog qhov txawv ntawm LiAlH4 thiab NaBH4.
NaBH4 yog sodium borohydride, uas tseem yog tus neeg sawv cev txo qis. Tab sis, nws yog ib qho kev txo qis uas tsis tuaj yeem txo cov esters, amides thiab carboxylic acids. Nws molar mass yog 37.83 g / mol.
Summary – LiAlH4 vs NaBH4
Ob leeg LiAlH4 thiab NaBH4 yog qhov tseem ceeb txo cov neeg ua haujlwm hauv cov txheej txheem organic synthesis. Qhov txawv ntawm LiAlH4 thiab NaBH4 yog tias LiAlH4 tuaj yeem txo cov esters, amides thiab carboxylic acids whereas NaBH4 tsis tuaj yeem txo lawv.
