Featured Research

from universities, journals, and other organizations

Chemistry riddle solved

Date:
July 9, 2013
Source:
Albert-Ludwigs-Universität Freiburg
Summary:
Chemists have explained the structure of a non-classical carbocation. They have captured the 2-norbornyl cation as a crystal and determining beyond doubt the structure of this unusual and instable carbon compound. The 2-norbornyl cation is a non-classical carbocation, a molecule with a positively charged carbon atom that enters into five instead of three bonds with other atoms.

A model of the crystal structure of the 2-norbornyl cation: Slow cooling to -233 degrees Celsius enabled the scientists to determine the molecule's structure.
Credit: © Ingo Krossing

With support from Prof. Paul von Rague Schleyer from the University of Georgia, USA, a team of researchers including Prof. Dr. Ingo Krossing, Dr. Daniel Himmel, and Franziska Scholz from the Institute of Inorganic and Analytical Chemistry of the University of Freiburg and Prof. Dr. Karsten Meyer from the University of Erlangen has succeeded in capturing the 2-norbornyl cation as a crystal and determining beyond doubt the structure of this unusual and instable carbon compound. The 2-norbornyl cation is a non-classical carbocation, a molecule with a positively charged carbon atom that enters into five instead of three bonds with other atoms. Their article in the journal Science has ended a 50-year-old controversy among chemists.

The structure of the 2-norbornyl cations is at odds with the common view of molecules, but indeed, it seems that certain chemical reactions can only be explained through the existence of this short-lived intermediate stage. Scientists succeeded long ago in synthesizing the molecule, but analyzing its structure is considerably more difficult. The reason is the rapid migration of the hydrogen atoms, even in isolated crystal. Up to now, this stumbling block has prevented scientists from furnishing clear evidence of precisely how the bonds are distributed in the molecule.

In their article, the researchers now describe the method that ultimately enabled them to conduct an x-ray structure analysis on the 2-norbornyl cation. This method involves guiding x-rays through a crystal and then determining the structure of the molecule on the basis of the diffraction of the rays. In this special case, the scientists also had to take the additional difficult step of slowly lowering the temperature by means of cyclical temperature changes in order to freeze the migrating hydrogen atoms in a resting position at the extremely low temperature of -233 degrees Celsius.

As early as 1949, Chemistry Nobel laureate Prof. Herbert Charles Brown criticized the first description of non-classical carbocations by the chemist Prof. Saul Winstein and demanded clear experimental evidence. Classical carbocations with up to three bonds and a positive charge were also long regarded as a pipe dream, and accounts of them were even censored in journals. In the 1960s scientists finally succeeded in detecting them with the help of spectroscopic methods thanks to the work of Chemistry Nobel laureate Prof. George Andrew Olah. In the case of the non-classical carbocations, on the other hand, the extraordinary bonding situation of the carbon and the distribution of the positive charge over several carbon atoms led to a decades-long scientific dispute among leading chemists over the existence of these compounds -- which has now finally been resolved by the findings of the Freiburg researchers.


Story Source:

The above story is based on materials provided by Albert-Ludwigs-Universität Freiburg. Note: Materials may be edited for content and length.


Journal Reference:

  1. F. Scholz, D. Himmel, F. W. Heinemann, P. v. R. Schleyer, K. Meyer, I. Krossing. Crystal Structure Determination of the Nonclassical 2-Norbornyl Cation. Science, 2013; 341 (6141): 62 DOI: 10.1126/science.1238849

Cite This Page:

Albert-Ludwigs-Universität Freiburg. "Chemistry riddle solved." ScienceDaily. ScienceDaily, 9 July 2013. <www.sciencedaily.com/releases/2013/07/130709124000.htm>.
Albert-Ludwigs-Universität Freiburg. (2013, July 9). Chemistry riddle solved. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2013/07/130709124000.htm
Albert-Ludwigs-Universität Freiburg. "Chemistry riddle solved." ScienceDaily. www.sciencedaily.com/releases/2013/07/130709124000.htm (accessed September 18, 2014).

Share This



More Matter & Energy News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) — The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
Powered by NewsLook.com
Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) — Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
MIT's Robot Cheetah Unleashed — Can Now Run, Jump Freely

MIT's Robot Cheetah Unleashed — Can Now Run, Jump Freely

Newsy (Sep. 16, 2014) — MIT developed a robot modeled after a cheetah. It can run up to speeds of 10 mph, though researchers estimate it will eventually reach 30 mph. Video provided by Newsy
Powered by NewsLook.com
Manufacturer Prints 3-D Car In Record Time

Manufacturer Prints 3-D Car In Record Time

Newsy (Sep. 15, 2014) — Automobile manufacturer Local Motors created a drivable electric car using a 3-D printer. Printing the body only took 44 hours. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins