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Saturday, February 2, 2019

DIBORANE-HYDRIDE OF BORONE-(B2H6):

INTRODUCTION:
Boranes are hydride of Boron and diborane is famous borane. It is gas and is highly inflammable in air and poisonous Diborane is used for preparing substances such as high energy fuel and propellants.
The main boranes are Nidoborane and Archanoborane.
Nidoborane (BnHn+4): Example B2H6, B3H7, and B4H8
Archanoborane (BnHn+6):  Example B2H8
Boranes are hydride of Boron and diborane is famous borane. It is gas and is highly inflammable in air and poisonous Diborane is used for preparing substances such as high energy fuel and propellants.

Other Methods:

(1)  B2H6 contains 4-Terminal H are bonded by Sigma bond and  remaining 2-H are bridging hydrogen’s and of these are broken then dimer become monomer.
(2) Boron undergoes sp3 hybridisation 3 of its sp3 hybridised orbitals contain one( e¯) each and fourth sp3 hybrid orbital is vacant.
(3) 3-(Three) of these sp3 hybrid orbitals get overlapped by s orbitals of 3-hydrogen atoms.
(4) One of the sp3 hybrid orbitals which have been overlapped by s orbital of hydrogen gets overlapped by vacant sp3 hybrid orbital. Of 2nd Boron atom. And it’s vice versa.

(5) By this two types of overlapping take place 4 (sp3– s) overlap bonds and 2(sp2 – s – sp3) overlap bonds.
(6) H is held in this bond by forces of attraction from B and This bond is called 3 centred two electron bonds (3C-2e bond) . Also called Banana bonds. Due to repulsion between the two hydrogen nuclei, the delocalised orbitals of bridges are bent away from each other on the middle giving the shape of banana.

(7) The two bridging hydrogens are in a plane and perpendicular to the rest four hydrogen..

ILLUSTRATED EXAMPLE (1): In Diborane
(A) 4 bridged hydrogens and two terminal hydrogen are present
(B) 2 bridged hydrogens and four terminal hydrogen are present
(C) 3 bridged and three terminal hydrogen are present
(D)None of the above

ILLUSTRATED EXAMPLE (2): Which one of the following statements is not true regarding diborane?
(A) It has two bridging hydrogens and four perpendicular to the rest.
(B) When methylated, the product is Me4B2H2.
(C) The bridging hydrogens are in a plane and perpendicular to the rest.
(D ) All the B–H bond distances are equal

ILLUSTRATED EXAMPLE (3): The structure of diborane (B2H6) contains
(A) Four (2C–2e–) bonds and two (2C–3e–) bonds
(B) Two (2C–2e–) bonds and two (3C–2e–) bonds
(C) Four (2C–2e–) bonds and four (3C– 2e–) bonds
(D )None of these

ILLUSTRATED EXAMPLE (4): The molecular shapes  of diborane is shown:
Consider the following statements for diborane:
1. Boron is approximately sp3 hybridised
2. B–H–Bangle is 180°
3. There are two terminal B–H bonds for each boron atom
4. There are only12 bonding electrons available
Of these statements:
(A ) 1, 3 and 4 are correct                  (B) 1, 2 and 3 are correct
(C) 2, 3 and 4 are correct                    (D) 1, 2 and 4 are correct

Physical Properties of Diborane:

Chemical Properties of Diborane:

Structure of "Inorganic Benzene" /Borazole/Borazine:

Structure of Boron Nitride:

Structure of Fulelrences:

Structure of Graphite:


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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