Conformational Analysis – Coursework – abigale charles
Search
Essays
Sign up
Sign in
Contact us
Tweet
Index
/Science
Conformational Analysis
CHEM 222 FALL SEMESTER 2015CONFORMATIONAL ANALYSISStudents would understand the conformations of alkanes & cycloalkanes by the study of conformational analysis. {WADE: Chapter 3-7→3-15}. There are two teaching videos uploaded onto the SGU Mediasite somewhere up in the “cloud” (address given @ the end of handout.) There are also videos on YouTube, Khan Academy etc. that you can access. Recall that a carbon-carbon single (σ) bond is formed by the overlap of cylindrically symmetrical sp3 hybrid orbitals. Therefore, rotation about the bond can occur without changing the amount of orbital overlap. The different spatial arrangements that result from rotation about a single bond are called Conformations. Molecules with different conformations are called “conformational isomers” or “conformers”. [pic 1](We start our study of the topic with ethane)The conformers produced by rotation about the carbon-carbon bond represent a “continuum” between the two extremes below: an eclipsed conformer (on the left) where all the hydrogens are “covered up” and a staggered conformer (on the right) where the hydrogens are as far apart from each other as possible. We use Newman projections to represent the three-dimensional spatial arrangements resulting from rotation about a σ bond. A Newman projection assumes the viewer is looking along the longitudinal axis of a particular C –C bond. The carbon in front is represented by a point (where three lines are seen to intersect), and the carbon at the back is represented by a circle. The three lines emanating from each of the carbons represent its other three bonds. (Above, Newman projection of the staggered conformer of ethane)[pic 2]
The staggered conformer of ethane is more stable than the eclipsed, and is therefore lower in energy than the eclipsed conformer. Factors which contribute to the greater stability are:Better electron delocalization stabilizes the staggered conformation; whereas repulsions between bonds on adjacent atoms destabilize the eclipsed conformation.[pic 3]Staggered bonds have no torsional strain, while eclipsed bonds produce the most torsional strain. (Each H-C-C-H unit in ethane is characterized by a “torsion angle”, the angle between the H-C-C plane and the C-C-H plane).The staggered conformation is lower in energy (12 kJ/mol) than the eclipsed conformation. Because of this energy difference, rotation about a carbon-carbon single bond is not completely free since an energy barrier must be overcome when rotation about the C-C bond occurs. However, the energy barrier in ethane is small enough (12kJ/mol) to allow continuous rotation. At any one time approx. 99% of the ethane molecules will be in the staggered conformation because of its greater stability, and only 1% will be in the less stable eclipsed conformation. (Notice that in the diagram @ bottom of page 1, the staggered conformers are at energy minima, whereas the eclipsed conformers are at energy maxima.) Butane (C4H10) has three carbon-carbon single bonds, and rotation can occur about each of them. The Newman projections below show the staggered and eclipsed conformers that result from rotation about the C1-C2 bond. (Notice that the carbon with the lower number is placed in the foreground in a Newman projection).[pic 4]
Continue for 6 more pages »
Read full document
Download as (for upgraded members)
Citation Generator
MLA 7
CHICAGO
(2016, 02). Conformational Analysis. EssaysForStudent.com. Retrieved 02, 2016, from
“Conformational Analysis” EssaysForStudent.com. 02 2016. 2016. 02 2016 <
"Conformational Analysis." EssaysForStudent.com. EssaysForStudent.com, 02 2016. Web. 02 2016. <
"Conformational Analysis." EssaysForStudent.com. 02, 2016. Accessed 02, 2016.
Essay Preview
By: abigale charles
Submitted: February 13, 2016
Essay Length: 1,690 Words / 7 Pages
Paper type: Coursework Views: 316
Report this essay
Tweet
Related Essays
Analysis of a Letter by Martin Luther King Junior
Martin Luther King Jr.: A Question Of Ethics A Letter from Birmingham Jail" was penned as a response to a letter that criticized Martin Luther
1,304 Words | 6 Pages
Analysis and Context of Bob Marley's Lyrics
Analysis and Context of Bob Marley's Lyrics A lifetime of inspiration and struggle is depicted through a poster I acquired not to long ago. The
1,782 Words | 8 Pages
Critical Analysis of "the Necklace" Short Story
Critical Analysis of "The Necklace" Short Story The short story, The Necklace, by Guy De Maupassant, follows the life of a woman and her husband
1,064 Words | 5 Pages
Critical Analysis of "the Minister's Black Veil"
Critical Analysis of "The Minister's Black Veil" The small, early American town that the story "The Minister's Black Veil" takes place in is a quite
416 Words | 2 Pages
Similar Topics
Analysis of Platos
Reebok swot analysis
Get Access to 89,000+ Essays and Term Papers
Join 209,000+ Other Students
High Quality Essays and Documents
Sign up
© 2008–2020 EssaysForStudent.comFree Essays, Book Reports, Term Papers and Research Papers
Essays
Sign up
Sign in
Contact us
Site Map
Privacy Policy
Terms of Service
Facebook
Twitter