Ditte’s reaction in halogen chemistry
I2 O5 is a powerful oxidizing agent, which oxidize CO molecule in quantitative analysis to convert CO2 molecule along with molecular iodine .
Wednesday, January 22, 2020
I2 O5 is a powerful oxidizing agent, which oxidize CO molecule in quantitative analysis to convert CO2 molecule along with molecular iodine .
Wednesday, January 8, 2020
Halogen elements definition .
There are
few electronegative as well as non metallic elements ,belongs to 17th
group in the modern periodic table, are known as halogen elements . Halogen
elements are fluorine, chlorine, bromine , iodine and astatine .
Among these
, fluorine and chlorine are colourless
gaseous elements , bromine is brown color liquid and iodine is violet
crystalline solid.
The name
‘halogen’ means salt producing .That is
they produced salt , when react with
metals .The salts of first three occur in the sea water.
Such as sodium chloride ( NaCl ) , calcium fluoride (
CaF2 ), silver bromide ( AgBr ) and potassium iodide( KBr ) etc .
Halogen elements in periodic table.
According to
modern periodic table , group 17th comprises of five elements ,
namely , fluorine, chlorine, bromine ,iodine and astatine which do not occur free in the nature , are known
as halogen elements .
In deed , fluorine,
chlorine, bromine and iodine have closely related properties and are known collectively as the halogen elements.
Halogen elements properties
General
electronic configuration of halogen elements are, ns2,np5 .That is the outer most shell of halogen atom
contains seven electrons .
Hence halogen element have tendency to gain one more electron to complete their octet .
Hence halogen element have tendency to gain one more electron to complete their octet .
Consequently,
halogen elements are non metal as well as strong electronegative . The electronegativity
of halogen elements decrease as we move
from top to bottom along a group .
Halogen
elements have high affinity for
electron, that is have a strong tendency to pick up electrons . For this reason
, they exhibits strong oxidizing power .
They can oxidize metal as
well as non metal . Although ,the oxidizing power decrease on moving down the
group .
Halogen elements reactivity
All the
halogen elements react with metals as well as with many non metals to form halides. Fluorine is the most reactive among
the halogen elements.
The reactivity decreases when we move from top to bottom
along a group .
For example,
with sulfur fluorine forms sulfur
hexafluoride , chlorine forms sulfur tetrachloride , bromine forms sulfur
dibromide whereas iodine does not react at all .
Another
example of halogen elements reactivity are the interaction of halogens with
water .
Fluorine react with water fast with explosion to form a mixture of ozone and oxygen .
Chlorine react with water in presence of sunlight and bromine react so much less readily, while iodine scarcely reacts with water .
The chemical reactions of chlorine and bromine elements with water under specific condition is shown below,
Chlorine react with water in presence of sunlight and bromine react so much less readily, while iodine scarcely reacts with water .
The chemical reactions of chlorine and bromine elements with water under specific condition is shown below,
All the
halogen elements react with hydrocarbons but their reactivity decreases with
increase in atomic number .
Fluorine is most reactive towards hydrocarbons.
It decompose hydrocarbon and release
free carbon atom .
Chlorine under goes substitution reaction with hydrocarbon. Bromine also shows substitution reaction with hydrocarbon but slowly . Iodine
react with hydro carbon under condition
.
Halogen elements Uses
There are a
large number of use of halogens elements . Halogen elements used both in
organic as well as in inorganic chemistry .
In organic chemistry , halogen
elements participate in nucleophilic and in addition reaction to produced
a large number of halogen containing compounds .
In inorganic
chemistry there are a huge number
of halogenated compounds . Most important compounds of halogen elements are
Halogen
elements is used in many organic
reaction to produced halogenated
compounds . Iodine and bromine is used
as laboratory reagents .
Halogen
elements is also used in every day our
life . Such as chlorine is used to purify water .Chlorine is also a part of
table salt ( NaCl ) , which is most
widely used chemical compound.
Fluorine is
used in different fluorides , which are added to water supplies to protect our
tooth decay .
Fluorine is also used to hardiest our enamel to prevent tooth. HF is used in glass industry to prepare different type of glass .
Fluorine is also used to hardiest our enamel to prevent tooth. HF is used in glass industry to prepare different type of glass .
Chlorine
compound that is bleaching powder is used to prevent the growth of bacteria . Chlorine is also used in paper making industry and plastics industry .
Bromine is
in photography, to prepare medicine , in
water purification and to prepare pesticides
and flame resistant plastics .
Iodine is
used mainly in iodometric and iodimetric titration and to prepare medicine ( tincture of iodine ) .
Which is the
strongest acid among HF, HCl, HBr and HI ?
The acidic
strength of halogen acid depends on the degree of ionization in aqueous
solution and also bond dissociation energy .
Generally,
the degree of dissociation decreases with increasing bond dissociation energy .That is with increasing bond dissociation enthalpy, acidic strength decreases.
Since, the increasing order of bond dissociation energy of halogen acids are ,
Therefore,
the increasing acidic order of the above halogen acids are ,
Consequently,
among the halogen acids (, HF , HCl , HBr
and HI ), HI is the strongest acid .
Summary :
Halogen elements definition .
Halogen elements in periodic table .
Halogen elements properties .
Halogen elements reactivity .
Halogen elements uses .
Which is the strongest acid among HF, HCl , HBr and HI acid ?
Summary :
Halogen elements definition .
Halogen elements in periodic table .
Halogen elements properties .
Halogen elements reactivity .
Halogen elements uses .
Which is the strongest acid among HF, HCl , HBr and HI acid ?
Wednesday, January 1, 2020
Schotten Baumann reaction .
The benzoylation of phenol is carried out in presence of aqueous NaOH or pyridine solution . Because , Benzoyl chloride does not hydrolysed by base .
So, the
benzoylation of phenol in presence of aqueous NaOH solution gives phenyl acetate . This reaction is known as Schotten Baumann
reaction.
Monday, December 23, 2019
Why is pyridine more basic than aniline?
The strength of basicity depends on the tendency to donate an electron to the electron deficient element, ion or group.
In case of aniline, the lone pair of electrons on nitrogen atom takes part in the resonance with the pi electron of benzene ring.
Tuesday, December 17, 2019
What is paracetamol?
Paracetamol or N-acetyl para aminophenol is an aromatic compound which is also known as acetaminophen.
Paracetamol is an analgesic as well as antipyretic non narcotic drugs . It is used as a medicinal drugs to treat pain and fever.
Tuesday, December 10, 2019
What is Friedel crafts alkylation reaction ?
When hydrogen atom of benzene ring be substituted by the alkyl group in presence of anhydrous aluminium chloride ( AlCl3 ) catalyst to produced alkyl benzene, then the reaction is is Friedel crafts alkylation reaction.
It is an example of aromatic electrophilic substitution reaction.
Thursday, December 5, 2019
Why is picric acid or 2,4,6-tri-nitro phenol more acidic than phenol?
2,4,6-tri nitro phenol is also known as picric acid .Picric acid is more stronger acid than phenol.
Because,
picric acid or 2,4,6-tri nitro phenol contains three strong electron
withdrawing – NO2 group.
Due to – I effect and – R effect of – NO2 group, the density of electron on oxygen atom of O – H group very much decreases.
As a result, oxygen atom attract O – H bonded electron towards itself . Hence O – H bond becomes more polar and more weak.
So, O –
H bond break very easily to release
proton ( H+ ). Consequently,
picric acid or 2,4,6-tri nitro phenol more acidic than phenol .
What is acidic order of o-nitro phenol , m-nitro phenol and p-nitro phenol and why?
All the mono nitro phenols are more acidic than phenol. Because – NO2 group is a strong electron withdrawing group .
Due to – I effect and – R effect, – NO2
group can attract electron from any position (ortho, meta or para). Hence,
all the mono nitro phenols are more acidic than phenol.
The acidic
order of mono nitro phenols with compare to phenol are,
Now, among the o-nitro phenol, m-nitro phenol and p-nitro phenol, only o-nitro phenol and p-nitro phenol can attract electron from - OH group due to – R effect of –NO2 group.
Because , due to presence of – NO2 group in
ortho and para position , a conjugation takes place between the lone pair of
oxygen atom of – OH group and – NO2 group through benzene nucleus
.
But, in case
of m-nitro phenol, - NO2 group present in meta position . Hence in
this case conjugation between lone pair of – OH group and – NO2
group does not occur.
So ,for meta
isomer, the density of electron of –OH
group decrease due to – I effect only .
Hence the
density of electron on oxygen atom is lowest for p-nitro phenol and highest for
m-nitro phenol. As a result , oxygen atom attract O – H bonded electron towards
itself .
Consequently,
the – OH bond for p-isomer becomes more polar and more weak . But the – OH bond
of m-nitro phenol becomes less polar.
So p-nitro phenol gives proton ( H+ )
more easily than the other two isomers .Hence the
acidic order of o-nitro phenol , m-nitro
phenol and p-nitro phenol are as follows,
Why o-nitro phenol and p-nitro phenol are more acidic than phenol?
O-nitro phenol and p-nitro phenol are more acidic than phenol. Because – NO2 group is a strong electron withdrawing group .
Besides this , for – R effect of – NO2 group , a conjugation takes place between the lone pair of oxygen atom of – OH group and – NO2 group through pi bond of benzene nucleus . Hence, oxygen atom gets partially positive charge.
As a result
, oxygen atom attract O – H bonded electron towards itself . Hence O – H bond becomes more polar and more weak .
So, O –
H bond of o-nitro phenol and p-nitro phenol break very easily to release proton (
H+ ) than phenol.
Consequently, o-nitro phenol and
p-nitro phenol are more acidic than phenol.
Practice problem:
What is acidic order of o-nitro phenol , m-nitro phenol and p-nitro phenol and why ?
Why is
picric acid or 2,4,6-tri nitro phenol more acidic than phenol ?
Why
o-nitro phenol and p-nitro phenol are more acidic than phenol ?
Monday, December 2, 2019
Phenol is acidic or basic?
Phenol is an aromatic alcohol, which contain – OH group.The lone pair electron on oxygen atom of phenol participate in resonance with the pi electron of benzene
nucleus.
Wednesday, November 27, 2019
Why boiling point of alcohol is higher than ether?
Oxygen is
more electronegative than hydrogen. For
this reason, O – H bond of alcohol is
polar one.
As a result , alcohol molecules can form inter molecular hydrogen
bond, through which alcohol molecules become associated and they are staying
as gigantic molecule.
Hence, a
large amount heat energy is required to break this large number of hydrogen
bond .Consequently,
the boiling point of alcohol molecule is very much higher.
Thursday, November 21, 2019
Why acetic acid is more acidic than phenol?
Both acetic acid and phenol are ionized in aqueous solution and give acetate and phenoxide anion respectively. Now ,the strength of acid depends on relative stability of their concerned anion ( conjugate base ).
Friday, November 15, 2019
Why ionic bond is non directional but covalent bond is directional?
Actually, there is no existence of ionic bond. Ionic bond is nothing but a force of electrostatic attraction between cationand anion, which is formed by the lose or gain of electrons.
Since there
is no direction of electrostatic attraction force, so ionic bond or ionic
valency has no specific direction.
Friday, November 8, 2019
Why CH3Cl is more active than C6H5Cl towards hydrolysis?
In case of chloro benzene, the lone pair of chlorine atom takes part in resonance with the Ï€ electrons of benzene ring . As a result, the C –Cl bond in chloro benzene gets partially double bond character .
