Glossary of Organic Chem Exam 2

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What is a radical?
An atom missing an octet
How is radical stability measured?
bond dissociation energies of cleaved C-H bonds
What is the substitution rule for stability of radicals?
primary < secondary < tertiary
How are radicals formed?
From covalent bonds by adding energy in the form of heat or light
Describe the selectivity and reactivity of bromination
selective, not very reactive
Describe the selectivity and reactivity of chlorination
non-selective, quite reactive
What is the rate determining step in a radical halogenation?
There IS no determining step.
Which step determines the product in a radical halogenation?
The first step.
Bromination: endothermic or exothermic?
Bromination: early or late transition state? Is the product stability important to Ea?
late; yes
Chlorination: endothermic or exothermic?
Chlorination: early or late transition state? Is the product stability important to Ea?
early; no
Which is better for a controlled synthesis, chlorination or bromination?
Bromination. It is more selective and you can get specific products. (unless there is only one possible product of chlorination, in which case it doesn't matter what is used)
What is special about the reactant N-bromo-succinamide (NBS)?
It is best to use for allylic bromination, because it only happens once instead of continuing to fill all spots on the molecule.
What do orbitals have to do with resonance?
Orbitals overlap, creating delocalized pi bonding which allows electrons to be shared over this pi bond cloud.
Define the following types of dienes: cumulated, conjugated, and isolated.
cumulated: both double bonds are to the same carbon
conjugated: double bonds separated only by a single bond, not by a carbon
isolated: double bonds separated by a carbon (and therefore also two single bonds)
What are the 4 rules for judging stability of resonance structures?
1.) More bonds and less formal charge = better resonance structure
2.)complete octets = better
3.) negative charge is best on most electronegative atom. positive charge is best on least electronegative atom.
4.)Use other concepts as needed

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