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Sunday, January 3, 2021

Methylation of Diborane (B2H6) replace only four hydrogen why ?

Methylation of Doborane:

(1) In diborane two boron atoms and four terminal hydrogen atoms lie in one plane. While two bridge hydogen atoms (encircled ) lie smmetrically above and below the plane.

(2) Total valence electrons in B2H6 is 12(6 from boron 3x2) and 6 from six hydrogen atoms) and there are two B-H-B (3C-2e) bridge bonds and four B-H (2C-2e) terminal bonds.

(3) Bond energy of B-H-B bond is 441 kj per mole which greater than bond energy B-H bond (341Kj per mole) hence methylation of diborane no more than four hydrogen.

(4) In above reaction it is clearly reveal that none of the bridge hydrogen in B2H6  has been replaced by –CH3 .ie in this reaction both the bridge bond remaine undissociate.

Related Questions: 

(1) Why aqueous solution of AlCl3 is acidic in nature ?

(2) What happen when aq AlCl3 react with Acid or Base?

(3) Although anhydrous aluminium chloride is covalent but its aqueous solution is ionic in nature. Why?

(4) Why BF3 do not exist as dimer?. Explain.

(5) Why B-F bond length in BF3 is shorter (130 pm) than B-F bond Iength in BF4- (143 pm)?. Explain.

(6) B-F bond length in BF3 is shorter than B-F bond length in (BF4)- why?

(7) When B2H6 is allowed to react with following Lewis bases, then how may given Lewis base form adduct through symmetrical Cleavage of B2H6.

(8) What is product of reaction between diborane (B2H6) and ammmonia (NH3)?

(9) Why methylation of Diborane (B2H6) replace four hydrogen only ?

(10) What is Use of Boric Acid?

(11) What is use of Orthoboric acids?

(12) What is basicity of "Boric acid" ?

(13) Why Boric acid exist in solid state ?

(14) What is structure of solid Ortho Boric acid ?

(15) What is effect of heat on Borax?

(16) What is the structure of trimetaboric acid and trimetaborate ion?

(17) What is the Sodium per borate ,give the structure and its uses?

(18) Why aqueous solution of borax reacts with two moles of acids ?

(19) What is the molecular formula of Borax ?

(20) Why Boric acid become strong acid in the presence of cis 1,2-diol or 1,3-diol ?

(21) Why Borazine is more reactive than benzene towards Electrophic Aromatic substitution reactions ?

(22) Why Borazine (B3N3H6) is also known as inorganic benzene ?.

(23) Four-center two-electron bond (4C-2e Bond): Structure of AlCl3:

(24) What is the difference between the structure of AlCl3 and diborane?

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