Three quick OC Questions from Destroyer

[Incis0r]

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Hi there! I would appreciate your help on 3 OC questions from the DAT Destroyer 2015 edition.

1. #13: Why would the para isomer crystallize out of solution and the ortho not? Also, how would column chromatography help separate the two...the way I see it, they both have dipole moments and are polar.

2. #20- The problem says that in steam distillation, the mixture distills at a temperature below the BP of the lower boiling component. I thought that distillation happens when the lower boiling component is vaporized while the higher boiling component isn't- so shouldn't it be above the BP of the lower boiling component?

3) #31- Why is choice B considered to have electron withdrawing groups? I thought NH2 was an activator/electron donor and that it was the most basic compound to the ones provided.

Thank you for your help in advance!

 

[DAT Destroyer]

Hi there! I would appreciate your help on 3 OC questions from the DAT Destroyer 2015 edition.

1. #13: Why would the para isomer crystallize out of solution and the ortho not? Also, how would column chromatography help separate the two...the way I see it, they both have dipole moments and are polar.

2. #20- The problem says that in steam distillation, the mixture distills at a temperature below the BP of the lower boiling component. I thought that distillation happens when the lower boiling component is vaporized while the higher boiling component isn't- so shouldn't it be above the BP of the lower boiling component?

3) #31- Why is choice B considered to have electron withdrawing groups? I thought NH2 was an activator/electron donor and that it was the most basic compound to the ones provided.

Thank you for your help in advance!

#13

The para isomer has the highest degree of symmetry, hence has the highest melting point. Column Chromatography is used all the time, since they all DIFFER in polarity. As a general rule, the ortho isomer has the greatest dipole.

#20

Many organic compounds tend to decompose at high sustained temperatures. Separation by distillation at the normal (1 atmosphere) boiling points is not an option, so water or steam is introduced into the distillation apparatus. The water vapor carries small amounts of the vaporized compounds to the condensation flask, where the condensed liquids phase separate, allowing for easy collection. This process effectively allows for distillation at lower temperatures, reducing the deterioration of the desired products.

Hope this helps.

Dr. Romano

 

[Incis0r]

#13

The para isomer has the highest degree of symmetry, hence has the highest melting point. Column Chromatography is used all the time, since they all DIFFER in polarity. As a general rule, the ortho isomer has the greatest dipole.

#20

Many organic compounds tend to decompose at high sustained temperatures. Separation by distillation at the normal (1 atmosphere) boiling points is not an option, so water or steam is introduced into the distillation apparatus. The water vapor carries small amounts of the vaporized compounds to the condensation flask, where the condensed liquids phase separate, allowing for easy collection. This process effectively allows for distillation at lower temperatures, reducing the deterioration of the desired products.

Hope this helps.

Dr. Romano

Thank you so much Dr. Romano!!! As always, your answers helped a lot.

 

[DAT Destroyer]

Thank you so much Dr. Romano!!! As always, your answers helped a lot.

#31

Hello Incis0r

😱WHOA WHOA WHOA.......you missed the key point !!!!!

Benzene is the Electron Withdrawing Group !!!!!!

This question asks about basicity,,,,focus on the NH2 group !! Groups attached to this such as benzene rings withdraw electrons AWAY from the Nitrogen. The NH2 is an electron donating group, but has nothing to do with this question. Basicity is generated from the electron pair residing on the Nitrogen atom .

Regroup yourself, and go over this again. 🙂

Hope this helps

Dr. Romano

 

[Incis0r]

#31

Hello Incis0r

😱WHOA WHOA WHOA.......you missed the key point !!!!!

Benzene is the Electron Withdrawing Group !!!!!!

This question asks about basicity,,,,focus on the NH2 group !! Groups attached to this such as benzene rings withdraw electrons AWAY from the Nitrogen. The NH2 is an electron donating group, but has nothing to do with this question. Basicity is generated from the electron pair residing on the Nitrogen atom .

Regroup yourself, and go over this again. 🙂

Hope this helps

Dr. Romano

Thank you Dr. Romano!!!