Nitroalkenes
| Classification of nitroalkenes |
|---|
 Example of a nitro group on the sp 3 -hybridized carbon atom based on 3-nitropropene |
 Example of a nitro group on the sp 2 -hybridized carbon atom based on 2-nitropropene |
Nitroalkenes are a group of chemical compounds that contain both a nitro group (NO 2 ) and an alkenyl group .
They can be divided into two groups depending on how the carbon atom to which the nitro group is attached is hybridized (see table).
properties
Since the nitro group is both strongly electron-withdrawing ( negative inductive effect ) and, as an electrophilic center, not very reactive , nucleophilic addition can take place on nitroalkenes in which the nitro group is bonded directly to an sp 2 -hybridized carbon atom .
Nucleophilic addition
As a result of the high electron density of the C = C double bond and the electron-withdrawing effect of the nitro group, nitroalkenes can easily enter into nucleophilic additions. An example of this is given below:
In the first step, a hydride anion of the sodium borohydride adds to the C = C double bond of the nitroalkene 1 to form the intermediate 2, which is similar to an enolate anion . This then takes up a proton of the methanol and forms the stable nitro group back, so that a nitroalkane 3 is formed.
synthesis
The synthesis of a 1-nitroalk-1-ene can be carried out starting from an aldehyde :
The aldehyde initially reacts with the addition of nitromethane and acetic anhydride in pyridine in an aldol reaction to form nitroaldol 1 . Subsequent elimination of water produces the desired 1-nitroalkene 2 .
Natural occurrence
The soldiers of the termite species Prorhinotermes simplex spray the depicted nitroalkene as a toxic agent to defend their nest. The workers of the species are equipped with an enzyme that reduces the toxic nitroalkenes to nitroalkanes that are harmless to termites , so that the soldiers do not injure their own workers in defensive battles.
Individual evidence
- ↑ Jürgen Falbe , Manfred Regitz (Ed.): Römpp Chemie Lexikon. 9th edition. Georg Thieme Verlag, Stuttgart 1990, ISBN 3-13-734909-5 , pp. 3029-3030.
- ↑ Jürgen Falbe, Manfred Regitz (Ed.): Römpp Chemie Lexikon. 9th edition. Georg Thieme Verlag, Stuttgart 1990, ISBN 3-13-734609-6 , pp. 104-105.
- ↑ a b c d Jonathan Clayden , Nick Greeves, Stuart Warren: Organic Chemistry. Springer-Verlag, Berlin / Heidelberg 2013, ISBN 978-3-642-34715-3 , pp. 687-688.