DMF, HCONMe2 , is an aproric solvent (has no H for H-bonding) with a moderately high dielectric constant and a high dipole moment. Thus, although it dissolves many ionic compounds, DMF does not do so by forming H-bonds with the anions. The salts are dissolved, chiefly through solvation of the cation by attraction to the end of the C-O dipole. The + end of the dipole is shielded within the molecule and can solvate the anion very weakly, if at all.
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Friday, February 28, 2020
Why not peroxide effect observed in case of addition of HCl or HI with alkene but it observed with HBr only?
The peroxide effect is not noted in the case of HCI or Hl. This is due to the fact that HCI bond is too strong to be broken to produce free radicals (430.5 kJ mol-1) than the HBr bond (363.7 kJ mol-1). Hl has a lower bond energy (296.8 kJ mol-1) and in case of the addition of HI although H-I bond is easily broken by homolysis, but the iodine atoms so produced immediately react to form iodine molecules rather than attacking the double bond of carbon atom in alkene.
°CH3 + HI -->. CH4 + I°
I° + I°---> I2
Sunday, February 23, 2020
Which of the following is a strongest acid among oxy acids of chlorine and why? "HClO, HClO2, HClO3, HClO4"
According to Bronsted
Lowery concept, a strong acid has weak conjugate base and vice
versa.
The given oxy acids of
chlorine HCIO, HCIO2, HClO3 and HClO4 and their conjugate bases are CIO-,
CIO2-, ClO3-, ClO4- respectively. These anions are stabilised to
greater extent, due to the presence of π-bond and lone pair, if number of
π-bond increase extent of stabilisation increase. In case of ClO- there is no π-bond hence if form less stable
conjugate base hence act as weak acid while in case of ClO4- it has three pπ-dπ bond which stablised greater extent and form more
stable conjugate base hence it conjugate acid (HClO4) is strongest
acid. Oxy acids of chlorine and their number of pπ-dπ bonds given as:
HOCI (0~Pπ-dπ)
HOCIO (1~Pπ-dπ)
HOClO2 (2~Pπ-dπ)
HOCIO3 (3~Pπ-dπ)
Thus overall order of
acidic strength of oxy acids of chlorine is as:
"HClO < HClO2 < HClO3 < HClO4"
Related Questions:
Topic:
17th Group HALOGENS FAMILY
How does the thermal stability of oxyacids of chlorine increase with an increase in the oxidation state of chlorine atom ?
The thermal stability of oxy acids of chlorine increase on increasing of oxidation number of chlorine atom because on addition of additional oxygen atoms, the number of (pπ-dπ) π-bonds increase which provide extra stability to the molecules. Oxy acids of chlorine and their number of pπ-dπ bonds given as:
HOCI (0~Pπ-dπ)
HOCIO (1~Pπ-dπ)
HOClO2 (2~Pπ-dπ)
HOCIO3 (3~Pπ-dπ)
Thus the overall stability of oxy acids of chlorine are given as:
"HClO < HClO2 < HClO3 < HClO4"
Related Questions:
Topic:
17th Group HALOGENS FAMILY
What is the correct order of electronegativity of Cl atoms in HClO, HClO2, HClO3 and HClO4 ?
According to the question the oxidation states of Cl are in given series of oxy acids as
follows:
HOCI (Chlorine +1 oxidation
state)
HOCIO (Chlorine +3 oxidation
state)
HOClO2 (Chlorine +5 oxidation state)
HOCIO3 (Chlorine +7 oxidation state)
The hydrogen is bonded
to an oxygen rather than to the chlorine in the given oxy acids. Now It is
clear that on addition of additional oxygen atoms with chlorine, it's oxidation
state also Increases hence acidity as well as electronegativity both increase
linearly.
We know that "Electronegativity is the property
of pulling the bonding electron pair towards itself". Higher the oxidation state means more
electrons attracted towards thus the atom has more oxidation state (+) is more
electronegative. So electronegativity of Cl follows:
"HCIO < HCIO2 < HClO3 < HClO4."
Related Questions:
Topic:
17th Group HALOGENS FAMILY
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