[physstudent1]

I understand that a cuprate reaction will react exclusively with 1,4 addition but I am not really sure what the diethyl ether and water will accomplish after??  there is no mechanism for this reaction in my book and only 1 example reaction which just has an acidic workup after...

[azmanam]

solvent

[physstudent1]

I tried just adding the ch2-ch3 to the tertiary carbon (which is 4) but its not correct?

[azmanam]

what do you get after step 1, before step 2?

[nj_bartel]

I can see why it woudl be confusing, as they numbered diethyl ether like it was a reactant.  Diethyl ether is a solvent, water is a reactant

[physstudent1]

3,3-dimethyl-pentanal?

[nj_bartel]

I'd agree with that answer.

While you're around azmanam, I don't understand why it is that soft nucleophiles do 1,4 addition while hard nucleophiles do 1,2 addition.  Is this just something that isn't teachable at the undergrad level?

[physstudent1]

my prof today said that the reason behind it was a little out of the scope of my course i think (im in Organic Chem 2nd semester) (undergrad of course).

[nj_bartel]

Ah ok.  I'm the same level as you, thanks.

[azmanam]

there's a whole unifying theory of hard/soft acid/base chemistry.  It's a lot of handwaving, and I don't fully understand it all, but it can be useful at times.

http://www.meta-synthesis.com/webbook/43_hsab/HSAB.html

Basically, to a first approximation, large, weak, relatively stable compounds (cuprates, etc) are weak, slower, they get pushed around by bullies.  They'll form the more stable product (Michael product, gives more stable C=O double bond).

Small, compact, high energy compounds (Grignards, organolithiums) are harder, more energetic and react at the kinetic site (1,2 addition, gives allylic alcohols).

I don't know if that helps or not.

[nj_bartel]

"Note that this Principle is simply a restatement of the experimental evidence which led to [the classification system in the first place]. It is a condensed statement of a very large amount of chemical information. As such it might be called a law. But this label seems pretentious in view of the lack of a quantitative definition of hardness.

I like your explanation better, for exactly the reason the article criticizes itself.  It spits out a bunch of data that they've noticed, but it doesn't really get into the theory of it.  Then again, I probably wouldn't be able to understand it without inorganic chem anyway.  Thanks