The compounds
or ions which doesn't follow octet rule inspite of that contains less than
eight electrons and also stable called Hypovalent species.
For examples BeF2,BF3, CH4+,
NF2+, B2H6, Be2Cl4
etc
Hypovalent
species may act as Lewis acid always.
The compounds
or ions which doesn't follow octet rule inspite of that contains less than
eight electrons and also stable called Hypovalent species.
For examples BeF2,BF3, CH4+,
NF2+, B2H6, Be2Cl4
etc
Hypovalent
species may act as Lewis acid always.
The compounds or ions
which doesn't follow octet rule inspire of that contains more than eight
electrons and also stable called Hypervalent species.
For examples XeFe2(10e),
XeFe4(12e), SF4(10e), SFe6(12e), IFe7(14e),
I2Cl6(10e), TeF5(12e) etc
Hypervalent species
may act as Lewis acid but not always.
P4, P4O4, P4O10, P4S3, P4S10, N4(CH2)6
The Oxides in which oxidation state of central atom is found to be one of the it's common oxidation state. The are also called acid anhydrides because on dissolving them into water oxygen acid is formed in which oxidation state of central atom is found to be same as present in Oxide.
Examples: B2O3, CO2, N2O3, N2O5, SO2, SO3, Cl2O7, XeO3, XeO4 etc.
The oxides in which calculated oxidation state of central
atom is more than maximum oxidation state of central atom due to the presence
of peroxide linkage.
For examples, H2O2, Na2O2, BaO2, PbO2, CrO5 etc.
The oxides contains more oxygen atoms as compare to central atoms
and according to valency requirements of central atoms number of oxygen atoms
are not sufficient.
For examples B2O3, C3O2,
C12O9, Pb3O, Rb9O2, Cs11O3
etc.
The oxides in which oxidation state of oxygen atom is found to be
it's uncommon oxidation state on central atom. Mixed oxides on dissolving in
water undergo "disproportionation"
For examples B2O3, ClO2, Cl2O7 , N2O5 , As2O4 etc.
Related Questions:
Which oxides (Anhydrides) gives two Oxyacids in water
?
What are the structural difference between oxides (
P4O6 and P4O10) of phosphorous?
What are common structural features of oxides (P4O6
and P4O5) of phosphorous?
Why Nitrogen
dioxide (NO2) dimerises to form Dinitrogen tetraoxide (N2O4)?
Why Nitrogen
dioxide (NO2) is coloured but Dinitrogen tetraoxide (N2O4) is colourless?
What is product
obtained when N2O5 is treated with NaCl?
What are the SESQUI OXIDES ? give the examples.
Which is more basic oxide ion (O-2 ) or hydroxide
ion( OH- ) and why ?
ABO3 type Oxides are also called Perovskite for examples CaTiO3 And
BaTiO3.
The oxides in which number of oxygen atoms pet central atoms is found to be 3/2 .And it may be ionic, covalent or missed oxides.Mostly M2O3 type Oxides (Corundum structure) are sesqui Oxides. Where M+2= Al, Ga, Ti, V, Cr, Fe, The etc.
Examples , B2O3, N2O3, Al2O3 ( covalent oxide) Fe2O3 (ionic oxide) Pb2O3 (mixed oxide)
The oxides in which
oxidati state of oxygen atom always -1/2, and super oxides are always ionic and
paramagnetic.
For
examples KO2 , PbO2, (NH4)O2 etc.
KO2 =>
k+[O-O]-. Have following character
Bond pair -2
Lone pair -2
Hybri- sp2, linear non
planner and bond angle not applicable.
The are oxides of non metals which are neither acidic
nor basic in nature or these are not
react with acids or bases for
examples.
CO, NO, N2O, H2O and OF2
etc.
According to this concept acids are any chemical species which react with bases and gives cations or accept anions or electrons.
Similarly Bases are a chemical species which react with acids and gives anions or electrons or cations
Hard and Soft acids and bases:
The Lux-Flood concept is given by Lux in 1929 and supported by Flood in 1947. Lux-Flood concept is based on oxide ion acceptor and donor tendency.
Lux-Flood bases: According to this concept bases are
those species which can donate oxide ions examples.
Lux-Flood Acids: According to this concept Acids are
those species which can accept oxide ions.
Chemical Reactions according Lewis acid-base concept:
Acid-base reaction in term Lux-Flood acid and base is a specific reactions in which oxide ions are mainly use in molten form or at high temperature.
Amphoteric Nature of Oxides as per Lux-Flood Concept:
Acidic Nature of Xenon
fluoride as per Lux-Flood Concept:
According to Lux –Flood concept Xenon
fluorides accept oxide ions from other compounds and insert fluorides ions in
its place.
For examples
The Order of decreasing Lux-Flood acidity of Xenon Fluorides is given as:
Limitations of Lux-Flood Acid –base Concept:
(1) It is
dealing with anhydrous reaction in fused molten oxides and other high temperature reactions found in
metallurgy and ceramics.
(2) When
Lux-Flood, acidic and basic of oxide react with water gives corresponding acid
and base.
Limitations of Lux-Flood Acid
–base Concept:
(1) Base
must contain oxide ion and acid must have accept oxide ions.
(2)It
fails to explain reaction without metal
ions
The most common concept of
acids and bases is due to Cady and Elsey. Most of the solvents undergo
auto-ionization and form cation and anions like water, regardless it contains
protons or not for examples; H2O, NH3, H2SO4, HNO3, POCl3,
BrF3, N2O4, NOCl, CH3COOH,
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?
What is product of reaction between diborane (B2H6) and ammmonia (NH3)?
Why methylation of Diborane (B2H6) replace four hydrogen only ?
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:
Electronegativity of F is much more than hydrogen and also hybridization of oxygen atoms in of H2O2 and O2F2 both have (sp3) same . According bent’s rule those hybrid orbitals containing flourine atom have less % s-characterand more p-character while other orbitals have more % s-character and less % s-character hence O-O bond length in O2F2 is shorter thane H2O2.
Related Questions:According to the bent's rule the more electronegative atom not only prefer to stay in that Hybride orbital which having less % S character (more p-character) but it also decreases % S-character and increases % P-character in its attached orbital from the central atom.
For example:C-H bond of CH4 is longer than C-H bond of floromethan
(CH3F) because In CH4 all the Sp3 hybrid orbitals are
equal in term of s-% character(25%) and %
p-charater(75%) so that all C-H bond in
CH4 are equal while in case
of CH3F the hybrid orbital has more p-character (more than 75%) and
less s-character (less then 25%) containg fluorine atom and other hybrid
orbitals have less p-character (less than75%) and more s-character (more than 25%)
hence C-H bond length of CH3F decreases.
EXCEPTIONS OF
BENT’S RULE:
(1):
Bent’s rule is applicable in those molecules where central
atoms are same and they are also in same
Hybridization.
For example N-N bond length cannot be compared in N2H4
and N2O4 using Bent rule.
(2): Bent’s rule violets in those molecules where steric
factor’s plays dominating rule.
Related Questions:
NH3, CH3NH2,
Pyridine , CO, T.H.F., PH3, PF3, (Me)3N, (Me)2NH.
SOLUTION:
B2H6 undergoes
symmetrical cleavage with large size weak Lewis base like PH3,
PF3, Pyridine , THF , (Me)3N , CO.
Related questions:
(1) Why Ga has small size than Al exceptionally
(2) Why aqueous solution of borax reacts with
two moles of acids ?
(3) What is structure of solid Ortho Boric acid
?
(4)What is the structure of trimetaboric acid
and trimetaborate ion?
(5) Why Borazine is more reactive than benzene
towards Electrophic Aromatic substitution reactions ?
(6) Why Borazine (B3N3H6)
is also known as inorganic benzene ?.
(7) Why B-F bond length in BF3 is
shorter (130 pm) than B-F bond Iength in BF4- (143 pm)?. Explain.
(8) Why B-F do not exist as dimer?. Explain.
(9) Although anhydrous aluminium chloride is
covalent but its aqueous solution is ionic in nature. Why?
(10) Why Boric acid become strong acid in the
presence of cis 1,2-diol or 1,3-diol ?
(11) Three-center two-electron bond (3C-2e Bond):Structure of AlCl3:
(12) What is the molecular formula of Borax ?
(13) What is the difference between the structure
of AlCl3 and diborane?
When a soluble aluminium salt is placed in water at room temperature. Initially the aluminium ion is surrounded by six water molecules and the complex ion has the predicted octahedral Geometry.
This complex ion behaves as an acid in water, losing protons, and a series of equilibria are established (H+ is used, rather than H3O+for simplicity):These equilibria give rise to an acidic solution in water, to the Hexahydroxoaluminate(iii) ion [Al(OH)6]3- in a strongly alkaline solution, and only in strongly acidic solutions is the hexaaquo ion [Al(H2O)6]3+ found.
The solid
hydrate, often written AlCl3. 6H2O and more correctly [Al(H2O)6]Cl3 can, therefore,
only be obtained from a strongly acidic solution. The reaction with water
resulting in the liberation of a proton is again known as hydrolysis and occurs whenever the
central metal ion is small and highly charged (i.e. having a high surface
density of charge), for example in salts of iron(III), chrornium(III).
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?
The fact that SF6
does not react with water is not due to thermodynamic stability. Rather, it is
because there is no low-energy pathway for the reaction to take place (kinetic stability).
Six fluorine atoms surrounding the sulfur atom
effectively prevent attack of water molecules and the sulfur atom has no
unshared pairs of electrons where other molecules might attack. In SF4
, not only is there sufficient space for an attacking species (water) to gain
access to the sulfur atom, but also the unshared pair is a reactive site. As a
result of these structural differences, SF6 is relatively inert,
whereas SF4 is very reactive.
The strength of a Lewis acid is a measure of its ability to attract a pair of electrons on a molecule that is behaving as a Lewis base. Fluorine is more electronegative than chlorine, so it appears that three fluorine atoms should withdraw electron density from the boron atom, leaving it more positive.This would also happen to some extent when the peripheral atoms are chlorine, but chlorine is less electronegative than fluorine. On this basis, we would expect BF3 to be a stronger Lewis acid. However,in the BF3 molecule, the boron atom uses sp2 hybrid orbitals, which leaves one empty 2p orbital that is perpendicular to the plane of the molecule. The fluorine atoms have filled 2p orbitals that can overlap with the empty 2p orbital on the boron atom to give some double bond character (Back Bond) to the B–F bonds.
As a result of the contribution by resonance structures having some double bond character, the boron atom in BF3 is not as electron deficient as it is in BCl3. And hence BCl3 a stronger Lewis acid than BF3
(1) π-bond fired by lateral (sidewise) overlapping
of atomic orbitals.
(2) lateral overlapping is only partial, so bonds
formed are weaker and hence more reactive than sigma bond.
(3) Free rotation about a π- bond is not possible.
(4) π- bond is weaker than sigma bond.
(5) π-bonds are non directional, so do not
determine the shape of a molecules.
(5) π- bond take part in resonance.
(6) π- bond formed by pure or anhybrid orbitals.
Importance difference in between 2p and 3p Orbitals is their energy.
The energy of atomic orbitals depends upon principal as well as azimuthal quantum number, which is more common known as (n+l) rule .
According to (n+l) rule the atomic orbital has less (n+l) value also has less energy vice versa.
If the value of (l):is same for two different orbitals then the greater the value of n greater is energy and vice versa.
For 2p => n= 2, l=0,. =>n+l= 2+0=2
For 3p => n= 3, l=0,. =>n+l= 2+0=3
Hence 3p have more energy than 2p orbital
The energy of atomic orbitals depends upon principal as well as azimuthal quantum number, which is more common known as (n+l) rule .
According to (n+l) rule the atomic orbital has less (n+l) value also has less energy vice versa.
For 2S => n= 2, l=0,. =>n+l= 2+0=2
For 2p => n= 2, l=2,. =>n+l= 2+1=3
Hence 2p have more energy than 2s orbital
The order of overlapping strength of orbitals is given as:
2pπ-2pπ>2pπ-3dπ>2pπ-3pπ>3pπ-3pπ.
The strength of π-bond is directly proportional to the overlapping strength of orbitals because on greater overlapping distance between two nuclei decreases and bond strength increase hence order of π-bond also given as:
2pπ-2pπ>2pπ-3dπ>2pπ-3pπ>3pπ-3pπ.
2pπ-2pπ, π-bonding is stronger than 2pπ-3dπ, π-bonding due to the lower energy gap (n=2) between them.
The importance comparison is in between 2pπ-3dπ and 2pπ-3pπ. The overlapping strength of 2pπ-3dπ is more than 2pπ-3pπ this is due to fact that , the 3d orbitals have two lobes which are more bent than 3p orbitals. That why overlapping strength increase.
(1) Oxygen of Me-O-Me is sp3 hybridised so C-O-C bond angle is more than 109’28” approx 110” due to crowding of methyl group.
(2) In disilyl ether , oxygen is Sp2 hybridised and planer due to
back bonding between oxygen and silicon atom. In this back bonding lone pair of oxygen atom
donate to the vacant d orbital of silicon atom due to this fact bond lengths of Si-O is
decrease and increases (approx 140”).
(3) In (Ph)3Si-O-Si(Ph)3 compounds Si-O-Si bond angle is Approx 180 due to back bonding and hybridisation is Sp.
Nitrogen (N) atom in trimethyl amine [N(CH3)3] is sp3 hybridised and tetrahedral ( bond angle ~107) due to non bonding electron pair of N is localised (more basic). On the other hand N atom of trisilyl amine [N(SiH3)3] is sp2 hybridised and trigonal planner (bond angle~120).This is due to the participation of non-bondlng pair of N into pπ-dπ back banding. Due to this delocalization of non-bonding electron pair of N in trisilyl amine it is also less basic