[georgina_009]

Which sentence characterises the following reaction?
       C=O            +ch3ch2 -MgBr        +H/H2O
CH3/   \CH2CH3    -------------->      ---------->

  a. This is a nucleophilic reaction by the very negatively polarised alkyl carbon in the Grignard reagent acting as the nucleophile. The alkyl group in the Grignard reagent reacts with the positively polarised carbonyl carbon of butanone.    
  b. This is an electrophilic reaction, in which the carboanion in the Grignard reagent reacts with the p -electrons in the carbonyl C=O double bond.    
  c. The +MgBr ion of the CH3CH2-MgBr acts as the electrophile and reacts with the p -electrons in the carbonyl C=O double bond.    
  d. The enol form of butanone, which has a C=C double bond, reacts with the electrophile, +MgBr, in the Grignard reagent.    
  e. This is a one-step teaction with the transition stete formed by the ketone and the Grignard reagent.    The energy profile of the reaction has only one activation energy hill.    

[alphahydroxy]

OK, firstly, this forum is not a place to other people to do your homework for you...

Also, it's MUCH MUCH MUCH MUCH easier to see what you're talking about if you use Isis/draw (free) or chemdraw to draw your reactions.

Ok, on to the chemistry! I think you should maybe have another look at the way you've drawn the grignard reagent - I'm not sure you've got the polarities the right way round (the issue of whether it's appropriate to draw this as an ionic species is probably not one you need to tackle...).

Now think about the reactivity of the carbonyl carbon - does it have a partial positive charge or partial negative charge? Is it an electrophile or a nucleophile?

Now think about the grignard reagent - how is the carbon-magenesium bond polarised? Will the carbon atom act as an electrophile or a nucleophile...?

If you've got the answers to these questions, you're pretty much there !

[AWK]

http://en.wikipedia.org/wiki/Grignard_reagent