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Optically active compounds can rotate the plane of polarised light. A polarimeter is used to determine, experimentally, if a compound is optically active or not.

Kaidor, Polarimeter (Optical rotation), CC BY-SA 3.0

1. Light source

2. Unpolarized light

3. Polarizer

4. Polarized light

5. Sample tube containing organic molecules

6. 30° optical rotation

7. Movable analyzer

8. Observer

Light is an electromagnetic wave that vibrates. When light vibrates in all directions it is unpolarised light. A polarizer is used to make the light polarised, i.e., the wave vibrates in a single direction. If a molecule is optically active, it rotates the plane of polarised light. A polarimeter…


Geometric isomers are formed when the rotation of the Carbon-Carbon bond is restricted either due to a double bond or the carbon-carbon single bond is a part of a chain.

There are two conventions to assign the configuration of a geometric isomer

  1. Cis and Trans
  2. E/Z (Including Cahn Ingold Prelog rules)

Cis and Trans

This notation is used when both carbons have the same substituent. If the substituents are on the same side, then the isomer is cis else it is trans.

The physical properties of cis and trans isomers vary.


Classification of Isomerism

Constitutional Isomers

These isomers differ in the arrangement of atoms. There are five types of constitutional isomers.

  1. Chain Isomers
  2. Functional Group Isomers
  3. Position Isomers
  4. Tautomers
  5. Metamers

Chain Isomers

Consider the molecular formula, C₅H₁₂. The possible structures are,


Carbon is a very unique atom. It has the ability to form four bonds and can form bonds with so many elements in the periodic table. This property of carbon along with its catenation has led to the formation of a separate branch of chemistry, Organic chemistry.

The versatility of carbon atom leads to variation in arrangement.

Before we learn about the concept of isomerism there are a few terms that need to be understood.

Molecular Formula

Molecular formula gives the information on the type and number of atoms in that particular molecule.

So, the molecular formula- C₂H₄ consists of…


As mentioned in the previous post, preliminary tests act as a base of qualitative analysis. In this step, the physical characteristics of the organic compounds are observed.The various tests are,

Colour

Small organic compounds are usually colourless. The colour in organic compound is due to the presence of a group called a chromophore.This group plays an essential part when we study the Ultra- violet spectra of organic compounds.

Odour

Certain functional groups show a characteristic odour. This can help us gauge the type of functional group present in the organic compound. For example, esters give off a fruity odour.

State


The analysis and identification of organic compounds in a lab is Qualitative analysis of organic compounds. An organic compound usually consists of Carbon, Hydrogen. These compounds may also contain oxygen, halogens, nitrogen, sulphur based on the functional group present.

We can divide the qualitative analysis into,

Preliminary tests

As the name suggests, these tests act as a base of the analysis. The preliminary tests consist of observing various physical characteristics such as color, odour, state, solubility and the ignition test. These tests help determine the steps to be followed.

Test for Extra Elements

Organic compounds contain other elements such as…


We know matter around us is classified into three states,

  • Solids
  • Liquids
  • Gases

In the gaseous state, the inter-molecular spaces are very high and the forces are low. They are highly compressible and also possess low densities.

Gas laws was taught to me in grade 11 and honestly, I never did understand how to remember it! When I was in college, one of my lecturers made it so simple and boy was it easy to remember! But before I start writing about the gas laws, let us look at the various physical properties of gases.

Gas laws might seem confusing…


Chemistry was initially quite difficult for me to understand. Here are a few basic concepts which when understood perfectly will help. I am assuming you have an idea about some things in chemistry.

Bonds

Organic compounds generally contain covalent bonds. These bonds are formed by sharing of electrons so that individual atoms get a stable configuration. It is of two types,

  • Sigma bond
  • Pi bond

Sigma bond is the strongest type of covalent bond which is formed by head on overlap of the atomic orbital.


When organic molecules are synthesized (even if it is 10 steps long), they are formed by these basic reactions. Once you understand the basic idea behind these reaction, it becomes easy to write the synthesis on your own.

In this post, I hope to give you a basic idea about the different types of organic reactions.

Addition Reactions

As the name suggests, this reaction involves the addition of a new group to a compound. Addition of the group is only possible after a double or triple bond breaks. So, the unsaturated compounds undergo this type of reaction.

A compound containing double bond…


For years I have had this interest towards both science and writing. One day when I was discussing career options with my English teacher (who was amazing) she told me that I could perhaps use my love for writing and mix it up with science. For years, I thought about it and decided to take a leap of faith and have started blogging.

Hi! I am Manasa. A teacher by profession and has a passion towards words.

I have completed my Masters in Organic Chemistry. A subject considered so so difficult but the subject I love. Over the course of…

V Manasa

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