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Showing posts with label 13th Group: BORON FAMILY:. Show all posts
Showing posts with label 13th Group: BORON FAMILY:. Show all posts

Tuesday, April 26, 2022

Banana Bond or 3C-2e Bond or Bridge bond or structure of B2H6 and Al2(CH3)6:

(1) Formation of 3C-2e bond in B2H6 is best explain by MOT and total number of bond in B2H6 is 6 (3C-2e=2 and 3C-4e=4)

(2) Bridge bonds are longer than terminal bond because at bridge bonds electrons are delocalized at three centres
(3) Bond energy (441kj/mole) of B-H-B bond is greater than bond energy (381 K j/mole) of   B-H bond.
(4) Hybridization of B atom is sp3, so non planer, and non polar (U=0)
(5)  B2H6 Methylated up to B2H2 Me4
(6) B2H6 is hypovalent molecule hence act as Lewis acid and undergoes two type of cleavage when react with Lewis base:

(A) UNSYMETRICAL CLEAVAGE: 
B2H6 Undergo unsymmetrical cleavage with small size strong Lewis base like NH3 NH2Me and NH (Me) 2 etc.

(B) SYMETRICAL CLEAVAGE:
B2H6 undergoes symmetrical cleavage with large size weak Lewis base like PH3, PF3,Me3N , OEt , OMe3, pyridine , THF , Thiophene , SMe2 ,Set2

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?

Monday, January 18, 2021

Consider the structure of Al2(CH3)3 given below and select the correct option?

(A) x < y

(B) alpha < Beta

(C) Bridge bond is formed by sp3-sp3-sp3 overlap.

(D) All of the correct.

Answer Key: (D)

Related Questions:

 (1) What is structure of diborane?

(2) What is structure of Al(CH3)3 and also explain the bridge bonding in Al(CH3)3?

(3) What is bridge bond ? explaine 3C-4e bridge bond with suitable examples .

(4) What is structural feature of monomeric and polymeric Beryllium halides ?

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

(6) What is structure of Beryllium chloride ?

(7) What is structure of BeH2 in solid state ?

What is structure of diborane?

(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 atoms.

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 only 12 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



Wednesday, January 13, 2021

What is the structure of Aluminium tetrahydridoborate (Al(BH4)3) ?

Al(BH4)3 is a volatile liquid and covalent compound and does not contain any ion but it contain (B-H-Al) hydrogen bridge structure in which each boron atom attach to aluminium by hydrogen bridge.


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?

Sunday, January 10, 2021

Structure of "Borazon" (Cubic boron nitride):

(1) In contrast to graphite, layered boron nitride is stable in air up to 1000°C, making it a useful refractory material. Layered boron nitride changes into a denser cubic phase at high pressures and temperatures (60 kbar and 3000 degree centigrade). And the denser and cubic form of this boron nitride is known as “Borazon”  and its structure is similar to diamond.

(2) The of “Borazon” is similar to that of diamond and it is stable at high temperature.

(3)The extreme hardness of Borazon is due to fact that the B-N bond. The B-N bond possess covalent character comparable to C-C bond of diamond and more important that B-N bond also some ionic stabilization due to electronegativity difference  boron and nitrogen atom.

Structure of "Inorganic Gaphite";

Structure of “Borazine/Borazole”/inorganic Benzene:

 Related Questions: 

Why aqueous solution of AlCl3 is acidic in nature ?

What happen when aq AlCl3 react with Acid or Base?

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

Why BF3 do not exist as dimer?. Explain.

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

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

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

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

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

What is Use of Boric Acid?

What is use of Orthoboric acids?

What is basicity of "Boric acid" ?

Why Boric acid exist in solid state ?

What is structure of solid Ortho Boric acid ?

What is effect of heat on Borax?

What is the structure of trimetaboric acid and trimetaborate ion?

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

Why aqueous solution of borax reacts with two moles of acids ?

What is the molecular formula of Borax ?

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

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

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

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

Tuesday, January 5, 2021

What is/are correct statement about Boroxine ion (B3O6-3) and Borazole (Inorganic Benzene)/ B3N3H6?

 (A) Both are planer and non polar

(B) Both have aromatic character

(C) Both have ppi-ppi bond formed by pairing of unpaired electrons

(D) Electrophilic subtitution  reaction occurs at B3N3H6

SOLUTION:( A,B,D) In Boraxine ion boron and oxygen atom alternatively combined to form six member ring and also each boron atom linked with extra oxygen atoms. Both boron and oxygen atoms have sp2 hybridization (by Back bonding and all oxygen atom involved in back bonding) and planer structure due to fact ring become aromatic but due to sp3 hybrisation of oxygen atom molecule become polar.


In Borazine (Inorganic Benzene) molecule, nitrogen is more electro negative than the boron. Nitrogen acquires partial negative charge and boron acquires partial positive charge and back bonding take place between boron and nitrogen.

Even though Borazine and Benzene have same stricture their chemical properties are different.

(1) Organic benzene is C6H6 while Inorganic benzene is Borazine having chemical formula B3N3H6

(2) Borazine is more reactive than Benzene with repect to electrophic addition reactions  due to high polarity (B-N polar bond) of Borazine plecules.

(3) Aromaticity of borazine is less than benzene  hence it is less reactive  toward Eectrophilic  substitution reactions than Benzene. 

Hence options (A), (B) and (D) is correct  But Option (C) is Incorrect Both have  pi-bond due to back bonding not due to formed by pairing of unpaired electrons

 Related Questions: 

Why aqueous solution of AlCl3 is acidic in nature ?

What happen when aq AlCl3 react with Acid or Base?

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

Why BF3 do not exist as dimer?. Explain.

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

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

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

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

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

What is Use of Boric Acid?

What is use of Orthoboric acids?

What is basicity of "Boric acid" ?

Why Boric acid exist in solid state ?

What is structure of solid Ortho Boric acid ?

What is effect of heat on Borax?

What is the structure of trimetaboric acid and trimetaborate ion?

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

Why aqueous solution of borax reacts with two moles of acids ?

What is the molecular formula of Borax ?

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

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

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

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

What is the difference between the structure of AlCl3 and diborane?

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?

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

Sodium per borate (NaBO3.H2O) (more correctly sodium dioxoborate peroxohydrate) is prepared from borax by treatment with NaOH to convert it to sodium borate (NaBO2) and further reaction with hydrogen peroxide.

Structure of sodium per borate:

What is Use of Boric Acid?

 Boric acid commonly known as TANKAN AMLA and use as Anti diaphoretic agent (anti sweating), Anti infective and also non-irritant agent. It is use in skin cream which provides nourishment and luster to the skin and also keeps soft, smooth and healthy Skin.

Boric acid also used in manufacturing of ENAMELS and Glazes for pottery and as disinfectants in medicine.

Saturday, January 2, 2021

Why aqueous solution of AlCl3 is acidic in nature ?

Aluminium forms covalent compound with chloride because lionization enthalpy (∆iH= +5137 kJ/mole) of Aluminium is very high due to small size and chlorine is unable to convert  Al into Al+3 ions. 

However, when anhydrous AlCl3 (which is covalent in character) is dissolved in water, it undergoes hydration as follow:  

AI2CI6 + H2O -->2[Al(H2O)6]+3 +(∆H)  

Hydration of anhydrous Aluminium chloride is highly exothermic in nature. The hydration enthalpy is more than ionisation enthalpy of aluminium.This hydration enthalpy removes all the three valence electrons of the aluminium leading to the formation of Al3+ more easly.This AI3+ is hydrated with water and form a complex ion. Thus in water Al exist as [Al(H2O)6]+3. so aqueous AlCl3 form Hexahydrated complex salt.

Related Questions: 

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

(2) Why Ga has small size than Al exceptionally

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

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

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

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

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

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

(9) Why B-F do not exist as dimer?. Explain.

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

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

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

(13) What is the molecular formula of Borax ?

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