Unit 4 Assessment Research

Disclaimer: This is a machine generated PDF of selected content from our products. This functionality is provided solely for your convenience and is in no way intended to replace original scanned PDF. Neither Cengage Learning nor its licensors make any representations or warranties with respect to the machine generated PDF. The PDF is automatically generated "AS IS" and "AS AVAILABLE" and are not retained in our systems. CENGAGE LEARNING AND ITS LICENSORS SPECIFICALLY DISCLAIM ANY AND ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES FOR AVAILABILITY, ACCURACY, TIMELINESS, COMPLETENESS, NON-INFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Your use of the machine generated PDF is subject to all use restrictions contained in The Cengage Learning Subscription and License Agreement and/or the Gale Academic OneFile Terms and Conditions and by using the machine generated PDF functionality you agree to forgo any and all claims against Cengage Learning or its licensors for your use of the machine generated PDF functionality and any output derived therefrom.

Chemists finally create elusive acid: textbook chemical cyanoform was sought for over a century Author: Beth Mole Date: Oct. 31, 2015 From: Science News(Vol. 188, Issue 9) Publisher: Science News/Society for Science and the Public Document Type: Brief article Length: 383 words

Full Text: After more than a century of effort, chemists have nabbed a legendary acid.

Cyanoform, or tricyanomethane, appears widely in textbooks as one of the strongest carbon-based acids. Yet despite repeated attempts to make the acid, cyanoform has evaded chemists until now. Researchers report September 18 in Angewandte Chemie International Edition that they isolated the acid by figuring out crucial experimental conditions.

The main problem was temperature, says Andreas Kornath, an inorganic chemist at Ludwig Maximilian University of Munich. Chemists had assumed that cyanoform is stable at room temperature. But using trial and error, Kornath and his team found that the acid is stable only below-40[degrees] Celsius.

[FORMULA NOT REPRODUCIBLE IN ASCII]

Cyanoform has a central carbon atom attached to a hydrogen atom and to three cyano groups, each consisting of a carbon triplebonded to a nitrogen. The molecule easily loses its hydrogen, making it a strong acid and demonstrating a rule of carbon acids-- electron-loving groups (the cyano groups) attached to a central hydrogen-toting carbon pull on that carbon's electrons. The molecule's electrons settle into a position close to the cyano groups, weakening the link to the hydrogen.

At room temperature, cyanoform decomposes, forming junk molecules, Kornath says. That probably happened when chemist Hermann Schmidtmann tried to make cyanoform in 1896. He mixed sulfuric acid with a stable relative of cyanoform called sodium tricyanomethanide. That molecule, a salt of cyanoform, has the same structure as the acid except it has lost the positive hydrogen ion, resulting in a negative molecule that is paired with a positive sodium ion.

Schmidtmann expected that sulfuric acid would stick a hydrogen atom onto the negative tricyanomethanide, forming cyanoform. Instead, he ended up with a concoction that probably contained only remnants of the unstable acid.

But at frigid temperatures, Kornath and colleagues made the acid. The team reacted a strong acid, hydrogen fluoride, with a salt of cyanoform. Multiple chemical analyses showed that the resulting molecule matched cyanoform's structure.

"It's very noteworthy," says physical chemist Daniel Kuroda of Louisiana State University in Baton Rouge. Theoretical chemistry cannot predict the temperatures at which substances decompose, he says. But experimental information like this gives chemists new ideas.

Caption: Try, try again At last, researchers have isolated cyanoform (chemical structure shown), a strong carbon acid, by making it at very cold temperatures.

Mole, Beth

Copyright: COPYRIGHT 2015 Science News/Society for Science and the Public http://www.sciencenews.org Source Citation (MLA 8th Edition) Mole, Beth. "Chemists finally create elusive acid: textbook chemical cyanoform was sought for over a century." Science News, vol.

188, no. 9, 31 Oct. 2015, p. 11. Gale Academic OneFile, link.gale.com/apps/doc/A433481330/AONE?u=lirn50909&sid=AONE&xid=cff24f81. Accessed 6 Feb. 2021.

Gale Document Number: GALE|A433481330