McMurry (Kap. 6,2) - How organic reactions occur: Mechanism Flashcards
(7 cards)
earlier we described what kinds of organic reactions there were, now explain how organic reactions occur.
How a reaction takes place is illustrated in a reaction mechanism.
- detailed showing which bonds break in what order, and which are formed in what order, and how many steps the reaction occur in.
All reactants used and products formed must also be included.
What two ways can a covalent two electron bond break?
- in a electronically symmetrical way: one electron remain with each product fragment (said to be homolytic)
- in a electronically unsymmetrical way: both bonding electrons remain with one product fragment (said to be heterolyctic).
What does a half headed arrow and a full headed arrow indicate in a reaction mechamism?
half headed arrow: the movement of one electron (symmetrical).
full headed arrow: the movement of two electrons (unsymmetrical).
In what two ways can a covalent two electron bond form?
- can form in a electronically symmetrical way: if one electron is donated to the new bond by each reactant (2 radikaler går sammen eksempelvis s.148).
- can form in a electronically unsymmetrical way: both bonding electrons are donated by one reactant,
What are processes that involve symmetrical bond breaking and making called?
Radical reactions.
A radical (also known as a free radical) is a species with an odd number of electrons, and an unpaired electron in its outer shell. This unpaired electron makes radicals highly reactive, as they tend to seek out other electrons to pair with.
What are processes that involve unsymmetrical bond breaking and making called?
Polar reactions.
Polar reactions involve species that have an even number of electrons and thus have only electrons pairs in their orbital - the most common form of reaction in both organic and biological chemistry.
In addition to radical and polar reactions, what also exist? A third one?
Yes, a pericyclic reaction, which will be further discussed in chapter 26.
