1 / 8

Azo Compounds

Azo Compounds. What are azo compounds?. Contain the -N=N- group. Where R and R’ are arene groups more stable than alkyl groups. Azo group is stabilised by becoming part of extended delocalised system. Result of a coupling reaction between a diazonium salt and a coupling agent. R-N=N-R'.

denis
Download Presentation

Azo Compounds

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Azo Compounds

  2. What are azo compounds? • Contain the -N=N- group. • Where R and R’ are arene groups more stable than alkyl groups. • Azo group is stabilised by becoming part of extended delocalised system. • Result of a coupling reaction between a diazonium salt and a coupling agent. R-N=N-R' Azo group

  3. N+N Cl- Diazonium salts • Only stable salts are aromatic - not particularly stable. • Lose -N+N as N2(g) • Electron rich benzene ring stabilises the -N+N group but decomposition occurs above about 5oC. • Add cold soln. sodium nitrite (NaNO2) to arylamine soln. In dilute acid below 5oC. • Diazotisation. • Prepare fresh and use immediately.

  4. + HNO2 + H+  N+N + 2 H2O NH2 How the salt is made. • Acid reacts with sodium nitrite to form unstable nitrous acid. • NaNO2 (aq) + HCl (aq)HNO2(aq) + NaCl (aq) • Nitrous acid reacts with the arylamine. phenylamine benzenediazonium ion

  5. Diazo coupling reactions • A diazonium salt reacts with another compound containing a benzene ring called a coupling agent. • Diazonium salt acts as an electrophile - reacts with benzene ring of coupling agent. • Coloured precipitate of azo compound immediately forms. • Important use as dyes.

  6. Coupling with phenols • Benzenediazonium salt and alkaline phenol gives a yellow orange azo compound • Benzenediazonium salt and alkaline naphthalen-2-ol gives a red azo compound.

  7. Coupling with amines • Diazonium salts couple with arylamines. • Benzenediazonium salt and phenylamine gives a yellow azo compound. • Use different diazonium salts and coupling agents to make different colours. • Azo compounds are stable so dyes do not fade.

  8. This powerpoint was kindly donated to www.worldofteaching.com http://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.

More Related