Wednesday, May 21, 2014

Elements and compounds

What is an element?

According to modern view, in simpler terms, an element can be defined as a substance made up of atoms of same atomic number.
For example, hydrogen gas, H2 is an element since the atoms in it have the same atomic number i.e. 1. 
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A chemical compound consists of two are more different types of atoms. For example, water is a compound made up of hydrogen and oxygen. Its formula is H2O i.e., there are two hydrogen atoms per every oxygen atom.

Monday, May 19, 2014

Electrolysis at adichemistry

Electrolysis involves dissociation (lysis) of an electrolyte by using a direct electric current.  In this process, electrical energy is used to carryout a non-spontaneous redox chemical reaction. 
The setup used to serve this purpose is known as electrolytic cell.
Read more at: 
http://www.adichemistry.com/physical/electrochemistry/electrolysis/electrolysis.html

electrolytic cell - a schematic representation

Wednesday, May 1, 2013

HYDROGEN BONDING

The electrostatic force of attraction between partially positively charged hydrogen in a polar molecule and an electronegative atom is called hydrogen bond.
It is represented by dotted line as shown below.
H--------X
where X is an electronegative atom.
Characteristics of Hydrogen bond 
1) The nature of H-bonding is purely electrostatic.
2) The hydrogen atom must be covalently bonded to a highly electronegative atom in order to acquire sufficient positive charge to participate in hydrogen bonding.
3) The electronegative atom should possess high charge density so as to attract positively charged hydrogen atom effectively. Thus H-bonding is observed with smaller and highly electronegative atoms such as F, O and N.
4) The hydrogen bond is stronger than van der Waal's forces of attraction. However it is weaker than the covalent bond and ionic bond.
5) The strength of H- bond is directly proportional to the electronegativity of electronegative atom. Thus the strengths of hydrogen bonds with different electronegative atoms varies as follows:
H------F > H------O > H-------N

Read more at: HYDROGEN BONDING

Tuesday, April 30, 2013

ETHYL CHLORIDE | ALCOHOLIC KOH | ELIMINATION | DEHYDROHALOGENATION


Why elimination occurs instead of nucleophilic substitution when ethyl chloride reacts with alcoholic potassium hydroxide?
Explanation:
Ethyl chloride can undergo both nucleophilic substitution as well as elimination reactions with strong alkali like KOH.
When it undergoes nucleophilic substitution, ethyl alcohol is formed as major product.
More at:
ETHYL CHLORIDE | ALCOHOLIC KOH | ELIMINATION | DEHYDROHALOGENATION

Sunday, November 11, 2012

200 solved problems in advanced organic synthesis for CSIR NET & GATE exams

As promised, the “Solved Problems in Advanced Organic Synthesis” book for CSIR NET & GATE exams is updated with 200 problems and is available freely to those who have purchased it previously. However, the rate is now revised to Rs. 875/-. Please download your updated version from the link I have provided at the time of purchase. Please mail me for the new password.
Further updates are NOT free. I have changed the policy. You need to participate in the discussions and help me to get further updates. Mail me for further details.

Click here to check the sample copy of Solved Problems in Advanced Organic Synthesis at Google docs