Organic Chemistry Chapt 14

What are conjugated compounds?
 compounds with alternating double and single bonds 
-found in pigments responsible for colors of fruit and flowers 
What do you call conjugated hydrocarbons with many double bonds?

 

 

Polyenes

(ex. Lycopene)

 

When conjugate alkenes react with HBr, HCl, and so on..the first step is protonation of one of the double bonds to form carbocation and then what is formed…?

 2 resonance…

1 with positive charge on # 2 carbon

1 with positive charge of # 4 carbon

(1,2 addition and 1,4 addition)

so the ending resulting in somewhere in between

Which addition happends at a temp of 0 degrees celsius? and 40 degrees celius?

0= 1,2 additions

40= 1,4 additions

What is a kinetic product? which reaction is this the result of?

this is a 1,2 addition that has lower activation barrier. 

*Cannot return to carbocation intermediate, irreversible

What is a thermodynamic product? 

Higher temp rxn that is reversible, 

*has enough energy to return to cation and reach equilibrium

*Will aslo favor the lower energy product regardless of hieght of activation barrier

*

What are Diels -alder reactions?

conjugated diens react with alkene (dienophile/diene lover) to form a six membered ring (hexagon)

 

* 1 step reactions with no intermediates!

Name 3 Good electron-donating groups  to put on dienes(EDG):

1.)ethers(OR)

2.)Alcohols (OH)

3.)Amines (NR2)

Name 3 Good electron withdrawing groups for dienophiles:

1.)Cyanogroups (CN)

2.)Nitro Groups (NO2)

3.) Carbonyl Compounds (ester, aldehydes, acids, ketones, and so on..)

What conformation is required for dienes?

S-Cis conformation…Both double bonds are on the same side of C-C single bond that seperate the two  double bonds bonds

*2 double bonds are in proper orientation to undergo reaction 

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what is this called?

Dien alder reaction
Dien alder reactions are sterioselective..what does that mean?

forms one stereoisomer over another…
Start with cis—-end with cis product

Start with trans—end with trans product 

What type of additionis used in the polymerization of the growing chain of a conjugated diene monomer?

 

 

1,4 addition

The initator (In) of a polymerization reaction of dienes can either be…

 

 

acid or a radical

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