Official DAT Destroyer Q&A Thread

[densaugeo]

Hi guys, since I'm currently going through the DAT Destroyer and I'm sure many of you guys are as well I felt this thread would be helpful. I usually have various questions while going through Destroyer regarding why a certain answer choice is correct or other times I am in need of a more detailed explanation.

Instead of making multiple threads each time we have questions, I thought we could just post them here and anyone can chime in with an explanation or further clarification.

Please don't post entire questions as that would be a violation of copyright. You can ask specific questions regarding a particular problem in the Destroyers.

Hopefully others find this a useful thread. Thanks!

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[DAT Destroyer]

Hello @orgoman22 . So I just finished going over content and have moved on to attacking actual problems. I have begun with the Organic Chemistry Odyssey. I'm looking at question #30 Chapter 1. Pretty basic stuff but I'm not sure why option (a) is one of the answers. Where is the ionic character to this compound? I see the formal charges you have assigned to each molecule but I only see non-metals. Am I missing a metal? or misunderstanding

Yes, you are missing a critical point. Usually, an ionic compound has a metal and a non-metal when the electronegativity difference is greater than 1.7. This is NOT a rule, but a great rule of thumb. Compounds such as BeBr2, and AlCl3 have a metal and nonmetal but are NOT ionic since the electronegative difference is under 1.7. Compounds with an NH4 moiety are always ionic because a large POSITIVE formal charge is placed on the Nitrogen atom. Any ion such as Cl- or I- would simply be there as a counterion. Thus, always be careful of a question like this......anytime you see a Nitrogen with 4 bonds, you know that it is ionic. This is reflected in such things as melting points and boiling points which would be very high for Ammonium salts.

Hope this helps.

Dr. Romano

 

[dl2501]

Dr. Romano,

If there was a compound that has both a ketone group and an ester group (or even a carb acid group), when it undergoes reduction, both the ketone and the ester group will be reduced. So to only reduce the ester group, a protecting group is normally used, like hoch2ch2oh to make an acetal to "hide" or "protect" the ketone group. But why wouldn't this protecting group act on the carbonyl carbon of the ester as well?

My reasoning for this would be that the carbonyl carbon on the ester is not as reactive than that on a ketone. The alkyl on a ketone is more donating than the electron withdrawing oxygens on the ester. Can you confirm?

Thank you.

 

[jLaws]

On DAT destroyer 2016, ochem section problem 70 it says that there will be a shift during the reaction of 2-methyl-1-propanol and HCl, so HCl could not be used to make 2-methyl-1-chloropropane. Since the alcohol is primary doesn't the reaction proceed via SN2 and thus not allow for shifts? Also on problem 47 an aldol addition is named as an aldol condensation which would not be a big error, but the problem asks which reaction and reaction name do not match and that was not the answer. The names are not interchangeable and the products would not be the same.

 

[jLaws]

Also, can anyone explain question 118 in the organic section? How are the hydrogens being abstracted and replaced with D without the presence of a base?

 

[PeteJook]

Dipole-induced dipole interactions occur when a polar molecule interacts with a non-polar molecule. There is a greater distortion of the electron cloud than that seen in a simple Van Der Waals interaction.

Van Der Waals Interactions occur when nonpolar molecules and polar molecules interact with each other, but is often very very weak.

Hope this helps

Dr. Romano

Why can water not hydrogen bond with the lone pair on one of the oxygens in CO2???

 

[jLaws]

Why can water not hydrogen bond with the lone pair on one of the oxygens in CO2???

I’ve started to forget this stuff, but I’m pretty sure it’s because co2 is linear and has no net polarity

 

[DAT Destroyer]

Why can water not hydrogen bond with the lone pair on one of the oxygens in CO2???

Both CO2 and H2O have two polar bonds. However, the dipoles in the linear CO2 molecule cancel each other out.....making it a NONPOLAR molecule. Essentially this means that the overall CO2 molecule lacks the electron density to form the needed hydrogen bond. Water will hydrogen bond with molecules that are polar such as alcohols or ammonia.........Hope this helps, Feel free to join our study group.

 

[JHF2020]

I am relatively new to SDN, but I do have a question on the 2018 DAT Destroyer in the Organic section. It is #267, which asks “Which works best for this reaction”? I narrowed it down to C & E, because I believe both of those would do E2. The answer in the book says C, because it prefers the less substituted alkene, but it looks to me that’s the only choice, so I don’t know why it’s favored over answer choice E.

 

[Vivian L]

In the 2017 DATDestroyer book, why is the answer C for question #201? I thought the the more molecules means more opportunities for collisions