Organic Chem Exam 2
Terms
undefined, object
copy deck
- 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?
- Endothermic
- Bromination: early or late transition state? Is the product stability important to Ea?
- late; yes
- Chlorination: endothermic or exothermic?
- 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