OCHEM 331 exam 3 ch 10

How do you name organohalides

1. Find longest chain
2. Number carbons of parent chain @ end where first substituent is
3. alphabetical order if same # carbon away

How can simple halides be prepared?

By reaction of alkane w/ Cl2 or Br 2 by radical chain pathway

Cl-Cl --hv-->

2Cl -

Alkyl Halide

Coupounds with a halogen atom bonded to a saturated SP3 hybridized carbon atom

Alkane Halogenation

poor synthetic method for preparing alkyl halides

- mixtures of products invariably result
- chlorination of methane doesn't stop

Hammonds postulate and relation to alkyl halides

Explanation of relationship btwn reactivity and bond strength

-more stable c.c. form faster than less stable in alkene elect. add. rxns

-more stable radical forms faster than less stable

Why is alkane bromination more selective for radical halogenation?

Rxn btwn Br is less exergonic
-stability of radical more important for Br than Cl

If have symmetry, then bromine attaches to...

the central carbon

NBS

in presence of light gives products result from substitution of H to Br by allylic position

allylic position

position next to the double bond

Why allylic position?

relative stabilities of various kinds of radicals

If electonically symmetrical, can be either of two resonance forms

-resonance hybrid of the two are correct

-greater the # of resonance forms, greater stability of a compound:
--bonding e- are attracted to the nuclei

allylic radical structure with two resonance forms =

more stable than typical alkylic radical (single structure)

allylic bromination of unsymetrical alkene =

mix of product (two)

products of allylic bromination reactions conversion into dienes by what?

dehydrohalogenation with a base

no symmetry =

attach at end

symmetry =

attach at center

What can be used for primary or secondary OH to best convert to alkyl halides and why

besides HCl...

-SOCl2
-PBr3

--less acidic and less likely acid catalyzed rearrangement than the HX method

What do alkyl halides react with when MG is used to make RMgX?

ether or THF

RMgX

alkylmagnesium halides
*****gringard reactions

What can grignard reagents be formed from?

alkenyl (vinylic)
aryl (aromatic)
-Cl, Br, or I (NO F)

C-MG bond is polarized or not?

polarized

what does polarized C-Mg make the grignard reagents

nucleophiles and basic

hydrocarbons are weak, then the carbon anions are...

STRONG BASES!!! (did you get this right...you suck if you didn't....)

If carbon anions are strong bases, then they react with what weak bases?

H20, ROH, RCO2H, and RNH2

grignard reaction

R-X -> R-MgX -> R-H

What is RLi prepared by

rxn of halide w/ Li metal

RLi rxns are simlilar to what other rxns?

alkyl Mg halides

gilman reagent

LiR2Cu, undergo coupling rxn with organo Cl, Br, and I (NOT F) to yield a hydro