Conformations of Ethane and Butane – Conformational Isomerism

Conformational isomerism is a form of stereoisomerism where interconversions of isomers are possible by rotations referring to single bonds. These isomers are termed as conformational isomers. Rotational energy acts as a barrier in the case of single-bond rotation. It has to be overcome to interconvert one conformer to another. The energy barrier must be small for Conformational Isomerism to occur.

There are several types of conformational isomers. For example, Ethane and Butane.

Conformations of Ethane

Ethane is an organic chemical compound. It is a colourless and odourless gas at a standard temperature. Ethane molecule consists of seven sigma bonds. There will be a change in the shape of the molecule when there is a rotation of about six carbon-hydrogen bonds. But many possible differences occur when there is a rotation about the carbon-carbon bond.

Conformational isomerism is a form of stereoisomerism where interconversions of isomers are possible by rotations referring to single bonds. These isomers are termed as conformational isomers. Rotational energy acts as a barrier in the case of single-bond rotation. It has to be overcome to interconvert one conformer to another. The energy barrier must be small for Conformational Isomerism to occur.

Suppose we rotate the CH3 group clockwise at an angle of 60 degrees; there would be a possibility that the hydrogen present at the front carbon is close to the hydrogen present at the back carbon. This is called eclipsed conformation.

Conformational isomerism is a form of stereoisomerism where interconversions of isomers are possible by rotations referring to single bonds. These isomers are termed as conformational isomers. Rotational energy acts as a barrier in the case of single-bond rotation. It has to be overcome to interconvert one conformer to another. The energy barrier must be small for Conformational Isomerism to occur.

Eclipse conformation is one of the highest conformations. Another clockwise rotation at an angle of 60 degrees would lead to a second eclipsed conformation. The solid line in the above figure represents the 6 carbon-hydrogen bonds that are extended at an angle of 120 degrees from 2 carbons.

Uses of Ethane: It is widely used in the production of ethylene. It is mainly done through steam cracking. It acts as a ripening agent for food. It is a primary ingredient in mustard gas.

Conformations of Butane

Butane is an organic compound which consists of an alkane with 4 carbon atoms. It may refer to a mixture of 3 isomers. At atmospheric pressure, butane is a gas. They are liquefied gas that is highly flammable.

Conformational isomerism is a form of stereoisomerism where interconversions of isomers are possible by rotations referring to single bonds. These isomers are termed as conformational isomers. Rotational energy acts as a barrier in the case of single-bond rotation. It has to be overcome to interconvert one conformer to another. The energy barrier must be small for Conformational Isomerism to occur.

Compared to ethane, hydrogen butane consists of a complex set of conformations that is related to the constitution. The below figure represents the 4 conformations of butane.

The above diagram explains the rotation of the C2-C3 bond due to the change in potential energy.

Uses of Butane: Pure form of butane can be used as a refrigerant. It is used in Butane Torches. It is widely used in gasoline blending. Butane Cartridges are used in powered cordless hair irons.

Frequently Asked Questions (FAQs)

Q1

What are the two conformations of ethane?

The two conformations of ethane are eclipsed conformation and staggered conformation.

Q2

What is the dihedral angle in eclipsed and staggered conformations of ethane?

The dihedral angle in eclipsed conformation is 0°, whereas the dihedral angle in staggered conformation is 60°.

Q3

Which is the most stable conformation of butane?

The anti-conformation is the most stable conformation of butane, as the bulky groups are separated by a dihedral angle of 180°.

Q4

Which is the least stable conformation of butane and why?

Eclipsed conformation is the least stable conformation of butane because the dihedral angle is 0°.

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.