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Old Dec 3rd 2012, 12:12 PM   #1
mxc120
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A Few Questions OchemII lab

I'm studying for my lab final, and am doing some practice /review problems.

1. The yield of triphenylmethanol is 30%. Give 2 reasons why the yield is low. Assume no mistake is makde, glass is dry, and oxygen side rxn is regligent. (Shows a grignard rxn).

Okay, so I put that 1. although the glass was dry, there might still be moisture in the air and 2. The 2 step process could make the yield low. If when making the grignard reagant the yield was 70 and then the other step the yield was 70 then a yield in the 30s makes sense. Is there something I'm missing?

2. Write the products of grignard reagent with water. I just have a benzene ring. Are the other products just a MgBr ion and the H ion and OH? Idk.

3. In the following rxn why do we have to use concentrated HNO3 and H2SO4? Shows Benzene w/ -c=O with -O-Ch3 also attached to the carbon reaxting with HNO3 and H2SO4 to make benezene with NO2 and same -c=O-o-ch3 attached.

I put that aromatic compounds only react with highly electrophilic compounds because the electrons of the pi system are less available because of the resonance in the ring structure. The electrophile NO2+ is electrophilic enough to add to the ring and it's made by heated concentrated sulfuric acid being added to nitric acid.

4. Write structure of the enolate formed from the following ketone. Under what conditions is an enolate generated? Shows acetophenone. I just moved the double bond from O to the C and C on the benezene and took away all the doulbe bonds in the ring? and made the O negative? For the conditions I put NaOH... it just has to be in basic conditions right?

5. Explain why enolate is not good for alkylation and acylation rxns. Okay I have no idea. I thought they could be used for these reactions.

6. Predict product of the following rxn: acetophenone + benezne with CH3 and -C=O attached in p positions with NaOH catalyst. Do they just combine? like the CH3 parts on each one?

7. Cyclohexanone rxts with pyrrolidine to form an enamine intermediate. Write the structure of the enamine. This reaction is done in toluene while toluene is constantly removed by distillation. Why do we distill toluene during this rxn?

okay all I can think of for why we're distilling it during the rxn is because it evaporates? In our lab book is just says that to be careful during the end evaporation during the end because you could potentially evaporate the whole thing, product included. As for the enamine I'm pretty sure I got that, it's a benzane w just 1 double bond and N on one end with the rest of the pyrrolidine.

Thank you so much for reading all this and helping me if you can!!
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Old Dec 4th 2012, 10:25 AM   #2
mxc120
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Update:

For number 2. I figured the products must be benzene ring & BrMgOh

and 7. 'Water is the other product produced during this rxn and azeotropic distillation of toluene removes this water, driving the reaction to the right and leading to a great amount of enamine to be produced"
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