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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[DentalNucleicAcid]

No.....A ring deviates out of planarity for many reasons. Consider Cyclooctatetraene...It has 8 pi electrons, but becomes non planar and tub-shaped to avoid being anti- aromatic. This molecule you are referencing is an annulene. Many annulenes are planar if and only if aromaticity is achieved. Thus a specie such as this having 14 pi electrons would be aromatic. Contrary to what you may have read in undergrad text books, the absolute planarity of a molecule is NOT required for aromaticity. , but aromaticity does decrease with decreasing planarity as exemplified with buckminsterfullerene. The bottom line is this...when dealing with large rings such as in problem 3, if you see conjugation, cyclic structure, and a Huckel number.....there is a very high probability the specie will be aromatic. A Google search of annulenes might interest you, or the Francis Carey text has wonderful examples as does text by Dr. Marc Loudon.

Hope this helps.

Dr. Romano

I see, thank you Dr. Romano

 

[Alikhan9]

Hey guys question 91 in general chemistry for the DAT Destroyer 2016, I am drawing a blank on simply how to approach this problem.

 

[Alikhan9]

So question 109 from the general chemistry 2016 Destoyer. "A 2.18 gram sample of hydrated XSO4 is heated to drive off all the water. The mass of the salt remaining was found to be 2.00 grams. How many water molecules are associated with each XSO4 molecule MW of XSO4 is 400g/mole?" If some one can not tell me the answer but how to approach this question like what would be the first step to do it is kinda tripping me up I set up the balanced equation for this and found the moles of XSO4 or if anybody could direct me to a video on this.

 

[asdf99]

IN a dieckmann condensation (ie: #305 in the 2016 destroyer), how do you know which alpha proton to deprotonate? Do you take from the less sterically hindered side?

 

[DAT Destroyer]

IN a dieckmann condensation (ie: #305 in the 2016 destroyer), how do you know which alpha proton to deprotonate? Do you take from the less sterically hindered side?

Yes....Remove the hydrogen from the least hindered side as the first move....then come in for the intramolecular attack !!!! For the DAT.....know the Dieckmann......Claisen....Aldol......Diels Alder.....Wittig.......Malonic Ester synthesis.....Grignard.....to name a few !!!!

 

[Dentoni]

Hello guys, In Question 119 from DAT destroyer math section. It is talking about interest and investment...The equation is set like this:
0.05X + 0.08 (18,000 - X) = 1,250

My question is: Why is it not written like: 0.08X + 0.05 (18,000 - X) = 1,250

Thank you guys for help

 

[DAT Destroyer]

Hello guys, In Question 119 from DAT destroyer math section. It is talking about interest and investment...The equation is set like this:
0.05X + 0.08 (18,000 - X) = 1,250

My question is: Why is it not written like: 0.08X + 0.05 (18,000 - X) = 1,250

Thank you guys for help

The question is asking how much interest she earned from bank B not bank A.
Your set up would be correct if the question asks for how much interest she earned from bank A.

 

[Dentoni]

Hi guys, Why does the switch happen to the back molecule of the Newman ?


Thank you for help

 

[Kstar007]

Organic Chemistry Question 283.
I must be wrong but I cannot seam to see the difference between answer choices A and E. I chose A and E is listed as the correct answer. The only thing I can think of is the way the bond angle were drawn to getter represent trigonal planer geometry.

 

[fit2]

I have a question too from the Destroyer BIO section Q213. So I suppose I'm looking for clarification where it says that
"heterozygotes do not have a trait" for autosomal recessive diseases. What about heterozygous for sickle cell anemia? I might be confused but doesn't heterozygous mean you have the trait, you just don't express it because you have the dominant one that's expressed?

Thanks a lot for the clarification. Just wanna understand even the small detaisl.
Also this post is amazing from what I see. Great work Dr. Romano and his wife and all the people who are helping answer questions. Big THANK YOU!!!

 

[fit2]

View attachment 206745

Hi guys, Why does the switch happen to the back molecule of the Newman ?


Thank you for help

So basically when you turn newman int ofisher projection to compare them to see if they are S/R you have to rotate around the sigma bond of the front carbon so that the CH3 are both pointing down. That way you get an eclipsed confirmation and you see the wedges and dashes sticking out to the right and left (when you look from the top of the molecule straight down). After you rotated the CH3 down then you turn the newman projection into a fisher and you put the front carbon on the top of the fisher projection. Then you assign stereochemistry rules and see that they two are actually diastereomers. I think this is the explanation. Let me know if you got it (or if I got something wrong)

 

[akimaki]

Is the carbocation-formation step always the slow/rate-determining step?

 

[M3mb3r13]

So basically when you turn newman int ofisher projection to compare them to see if they are S/R you have to rotate around the sigma bond of the front carbon so that the CH3 are both pointing down. That way you get an eclipsed confirmation and you see the wedges and dashes sticking out to the right and left (when you look from the top of the molecule straight down). After you rotated the CH3 down then you turn the newman projection into a fisher and you put the front carbon on the top of the fisher projection. Then you assign stereochemistry rules and see that they two are actually diastereomers. I think this is the explanation. Let me know if you got it (or if I got something wrong)

 

[DentalNucleicAcid]

Hi Dr. Romano,

I'm a bit a confused about the bromination/chlorination of aniline. I'm aware that aniline does not require a catalyst like FeBr3 to brominate, and that it would become trisubstituted in the absence of a protecting group like RCOCl. I also understand that aniline or nitrobenzene cannot do FC alkylation/acylation due to the reaction with the FeBr3 catalyst. But you stated here that you can in fact brominate aniline in the para postion in the presence of a catalyst:

The tri- substituted product is obtained in high yield. The reaction may go with using FeCl3 or just plain water due to the high reactivity. Consult any organic text book and look at the yield it would probably be over 90 percent in favor of the tri - substituted product. Even though you see 3 bromines it is not easy to stop the reaction at a single or double substituted product....as you can see a tri - substituted product results.

What I mean is, shouldn't the bromination of aniline in the presence of a catalyst not be able to proceed because of the reaction with the catalyst as in FC alkylation and acylation?

 

[DAT Destroyer]

I have a question too from the Destroyer BIO section Q213. So I suppose I'm looking for clarification where it says that
"heterozygotes do not have a trait" for autosomal recessive diseases. What about heterozygous for sickle cell anemia? I might be confused but doesn't heterozygous mean you have the trait, you just don't express it because you have the dominant one that's expressed?

Thanks a lot for the clarification. Just wanna understand even the small detaisl.
Also this post is amazing from what I see. Great work Dr. Romano and his wife and all the people who are helping answer questions. Big THANK YOU!!!

By trait, we mean a Heterozygous person does not show the phenotype of the disease.

 

[DAT Destroyer]

Hi Dr. Romano,

I'm a bit a confused about the bromination/chlorination of aniline. I'm aware that aniline does not require a catalyst like FeBr3 to brominate, and that it would become trisubstituted in the absence of a protecting group like RCOCl. I also understand that aniline or nitrobenzene cannot do FC alkylation/acylation due to the reaction with the FeBr3 catalyst. But you stated here that you can in fact brominate aniline in the para postion in the presence of a catalyst:

What I mean is, shouldn't the bromination of aniline in the presence of a catalyst not be able to proceed because of the reaction with the catalyst as in FC alkylation and acylation?

The reaction is like a BULLET !!!!! It is so hard to control.....that a catalyst is not even needed !!!!! Through the years.....I never even used FeBr3...but plain water !!!!!! If you wanted to add the Br onto only one position...you would need to protect the NH2 group with acetylchloride ..then brominate....then remove the protecting group . The David Klein book shows this nicely if your want to pursue this.

Hope this helps.

 

[fit2]

By trait, we mean a Heterozygous person does not show the phenotype of the disease.

I understand. Thank you!!!

 

[Sandel]

Hi Dr. Romano, thank you so much for helping us out!

Could you please explain OCHEM destroyer (2016):
#10 Is the answer the Amide functional group simply because we received 0 degrees for unsaturation? How should we go about solving these types of problems? What do you mean by comparing it to the nearest alkane?

#11 what is the job of the K2Cr2O7 reagent? Which is the name of the reaction this problem is under?

#12 will the PCC reagent always create this product? What is the name of this reaction under?

#13 how did you know the pka for the proton was -6? Do you first look at the elements the hydrogens are connected to in each compound or do you make conjugate bases of each one and then compare to pka table? How can you solve these problems fast?

#57 which peaks do you suggest we memorize for the IR spectra type questions?
#319 how can you tell which is most acidic?
#318 what do you mean by isomeric?

#7 how do you know where to place the Br in the three arrangements if it is monobrominated? Does this mean that the number of rings in a compound corresponds to the number I have monobrominated compounds as in two rings in naphthalene means 2 monobrominated compounds ect.?

 

[farzi2492]

DAT Destroyer 2016 Gen Chem Q: 28

I don't understand how we know the solution is dilute and how 1 x 10^-12 + 1 x 1o^-7 = 1 x 1o^-7

 

[fit2]

DAT Destroyer 2016 Gen Chem Q: 28

I don't understand how we know the solution is dilute and how 1 x 10^-12 + 1 x 1o^-7 = 1 x 1o^-7

It's because neutral water has a pH of 1 x 10^-7. If you add 1 x 10^-12 hydrogen ions that will impact the whole pH to such a small extent that the pH will virtually not change. Feralis makes a good analogy a few posts earlier about this questions: like if you have a million dollars and you add a few cents, your sum of money doesn't change you still have a million dollars. It's a tricky question. I remember the first time I heard it in Gen Chem I felt overwhelmed by the acid base chapter haha. Just keep at it and you'll learn to notice very small nuances.

 

[Kstar007]

Gen. Chem #125
How do you get 961 as the final answer. The explanation shows W=-4(-24) but that comes out to 96. Also how does the 10KJ of energy being released as heat come into play?

 

[fit2]

Gen. Chem #125
How do you get 961 as the final answer. The explanation shows W=-4(-24) but that comes out to 96. Also how does the 10KJ of energy being released as heat come into play?

Pretty sure it's a mistake. It should be 96.1 atm if anything I think

 

[DAT Destroyer]

Gen. Chem #125
How do you get 961 as the final answer. The explanation shows W=-4(-24) but that comes out to 96. Also how does the 10KJ of energy being released as heat come into play?

The answer 96 liters -atm.....it is NOT a one but the units of volume !!!! You need to look closer. The work done only depends on pressure and volume.....not heat released.

Hope this helps.

 

[DAT Destroyer]

DAT Destroyer 2016 Gen Chem Q: 28

I don't understand how we know the solution is dilute and how 1 x 10^-12 + 1 x 1o^-7 = 1 x 1o^-7

This is not hard......get out a calculator and see for yourself...... when 1 x 10^-12 is added to 1 x 1o^-7 the result is about 1 x 1o^-7 because the first value is so SMALL !!!!! Please reassure yourself of this.

Hope this helps.

 

[DAT Destroyer]

Hi Dr. Romano, thank you so much for helping us out!

Could you please explain OCHEM destroyer (2016):
#10 Is the answer the Amide functional group simply because we received 0 degrees for unsaturation? How should we go about solving these types of problems? What do you mean by comparing it to the nearest alkane?

#11 what is the job of the K2Cr2O7 reagent? Which is the name of the reaction this problem is under?

#12 will the PCC reagent always create this product? What is the name of this reaction under?

#13 how did you know the pka for the proton was -6? Do you first look at the elements the hydrogens are connected to in each compound or do you make conjugate bases of each one and then compare to pka table? How can you solve these problems fast?

#57 which peaks do you suggest we memorize for the IR spectra type questions?
#319 how can you tell which is most acidic?
#318 what do you mean by isomeric?

#7 how do you know where to place the Br in the three arrangements if it is monobrominated? Does this mean that the number of rings in a compound corresponds to the number I have monobrominated compounds as in two rings in naphthalene means 2 monobrominated compounds ect.?

#10 Is the answer the Amide functional group simply because we received 0 degrees for unsaturation? How should we go about solving these types of problems? What do you mean by comparing it to the nearest alkane?

You first need to calculate the degree of unsaturation. You can do this several ways, as shown in all the text books. However, my professor did it in a fast and more efficient way. I have shown this in the DESTROYER book. Compare the compound to the nearest alkane. Count hydrogens, carbons, and halogens as if they were hydrogens. Do not count Oxygens......for N subtract one H for each N. Our molecule is C20H44N2O. Thus, think of it as C20H42. Notice how I didnt count the O and subtracted the two N's. OK...now compare this to the nearest alkane...which is C20H42. Clearly we see that there is no hydrogen difference, hence 0 degrees of unsaturation. An amide cannot be possible, since it contains a double bond and therefore one degree of unsaturation. If you cannot follow this, please get the David Klein Organic text which does a nice job in explaining this. Hope this helps.

 

[DAT Destroyer]

Hi Dr. Romano, thank you so much for helping us out!

Could you please explain OCHEM destroyer (2016):
#10 Is the answer the Amide functional group simply because we received 0 degrees for unsaturation? How should we go about solving these types of problems? What do you mean by comparing it to the nearest alkane?

#11 what is the job of the K2Cr2O7 reagent? Which is the name of the reaction this problem is under?

#12 will the PCC reagent always create this product? What is the name of this reaction under?

#13 how did you know the pka for the proton was -6? Do you first look at the elements the hydrogens are connected to in each compound or do you make conjugate bases of each one and then compare to pka table? How can you solve these problems fast?

#57 which peaks do you suggest we memorize for the IR spectra type questions?
#319 how can you tell which is most acidic?
#318 what do you mean by isomeric?

#7 how do you know where to place the Br in the three arrangements if it is monobrominated? Does this mean that the number of rings in a compound corresponds to the number I have monobrominated compounds as in two rings in naphthalene means 2 monobrominated compounds ect.?

#11 what is the job of the K2Cr2O7 reagent? Which is the name of the reaction this problem is under?

K2Cr207 is potassium dichromate and is the MOST COMMON......MOST POPULAR.....and MOST IMPORTANT oxidizing agent employed in all of Organic Chemistry. It is presented in every text book. It will convert a primary alcohol to a carboxy acid and a secondary alcohol to a ketone. Please study !!!! Hope this helps.

 

[DAT Destroyer]

Hi Dr. Romano, thank you so much for helping us out!

Could you please explain OCHEM destroyer (2016):
#10 Is the answer the Amide functional group simply because we received 0 degrees for unsaturation? How should we go about solving these types of problems? What do you mean by comparing it to the nearest alkane?

#11 what is the job of the K2Cr2O7 reagent? Which is the name of the reaction this problem is under?

#12 will the PCC reagent always create this product? What is the name of this reaction under?

#13 how did you know the pka for the proton was -6? Do you first look at the elements the hydrogens are connected to in each compound or do you make conjugate bases of each one and then compare to pka table? How can you solve these problems fast?

#57 which peaks do you suggest we memorize for the IR spectra type questions?
#319 how can you tell which is most acidic?
#318 what do you mean by isomeric?

#7 how do you know where to place the Br in the three arrangements if it is monobrominated? Does this mean that the number of rings in a compound corresponds to the number I have monobrominated compounds as in two rings in naphthalene means 2 monobrominated compounds ect.?

#318 what do you mean by isomeric?

For 318......isomeric means that the two compounds are ISOMERS.....they have the same molecular formula, but differ in structure. Hope this helps.

 

[DAT Destroyer]

Hi Dr. Romano, thank you so much for helping us out!

Could you please explain OCHEM destroyer (2016):
#10 Is the answer the Amide functional group simply because we received 0 degrees for unsaturation? How should we go about solving these types of problems? What do you mean by comparing it to the nearest alkane?

#11 what is the job of the K2Cr2O7 reagent? Which is the name of the reaction this problem is under?

#12 will the PCC reagent always create this product? What is the name of this reaction under?

#13 how did you know the pka for the proton was -6? Do you first look at the elements the hydrogens are connected to in each compound or do you make conjugate bases of each one and then compare to pka table? How can you solve these problems fast?

#57 which peaks do you suggest we memorize for the IR spectra type questions?
#319 how can you tell which is most acidic?
#318 what do you mean by isomeric?

#7 how do you know where to place the Br in the three arrangements if it is monobrominated? Does this mean that the number of rings in a compound corresponds to the number I have monobrominated compounds as in two rings in naphthalene means 2 monobrominated compounds ect.?

#319 how can you tell which is most acidic?

The compound that is most acidic will be the one that yields the MOST stable ANION.......clearly choice c is the answer. As explained in the solution......the anion is AROMATIC !!!!! It has a 6 pi electron system. For a nice review of this, I suggest a glance at the David Klein text. Review the chapters on Acid-Base and Aromaticity. These areas do appear in full force on the DAT exam. Hope this helps.

 

[desertrat12]

First off, DAT Destroyer is awesome.

Question regarding #282 and #334 in 2016 edition:

#282 uses Torr and #334 uses mmHg. In 334, mmHg is converted to atm in the answer, however in 282 there is no converting the Torr back to atm. I'm confused at when this conversion is necessary vs when it isn't?

 

[DAT Destroyer]

First off, DAT Destroyer is awesome.

Question regarding #282 and #334 in 2016 edition:

#282 uses Torr and #334 uses mmHg. In 334, mmHg is converted to atm in the answer, however in 282 there is no converting the Torr back to atm. I'm confused at when this conversion is necessary vs when it isn't?

When using the combined law......it doesn't matter what units you use..as long as both sides have the same units. Working in torr or mmHg is fine. However,,,when using the Ideal Gas Law....or a law such as P.MW = DRT....R is a gas law constant........thus pressure MUST be in ATM !!!!!!! R has the value of .082 atm.l/moles K. Note the units of the constant !!!

This is extremely important. Remedy this IMMEDIATELY.

Hope this helps.

Dr. Romano

 

[desertrat12]

When using the combined law......it doesn't matter what units you use..as long as both sides have the same units. Working in torr or mmHg is fine. However,,,when using the Ideal Gas Law....or a law such as P.MW = DRT....R is a gas law constant........thus pressure MUST be in ATM !!!!!!! R has the value of .082 atm.l/moles K. Note the units of the constant !!!

This is extremely important. Remedy this IMMEDIATELY.

Hope this helps.

Dr. Romano

Makes perfect sense, thank you!

 

[Kstar007]

abc

 

[BrettRef54]

Organic Chemistry Destroyer 2016 Edition #293

It says to give the enantiomer of the molecule depicted. Shouldn't the #2 carbon be S because the Br is first then the COOH which is going in the R direction but the H is horizontal which is bad so we need to reverse it to S (and then the enantiomer would be R). In the answer key it says the opposite.

Thanks for the help

 

[DAT Destroyer]

Organic Chemistry Destroyer 2016 Edition #293

It says to give the enantiomer of the molecule depicted. Shouldn't the #2 carbon be S because the Br is first then the COOH which is going in the R direction but the H is horizontal which is bad so we need to reverse it to S (and then the enantiomer would be R). In the answer key it says the opposite.

Thanks for the help

This is your lucky day,,,,,Aren't you glad you are using DESTROYER to get blasted before it happens on the DAT ??? It is best to make errors like this in practice...and DESTROY the real exam. No...Br is Priority group number 1.. BUT......the R group above you has a C with a Cl......making in group priority #2...COOH is # 3....Tricky indeed. LOOK CLOSER...you missed it. REDO THIS PROBLEM !!!!!!!

Hope this helps.

Dr. Romano

 

[BrettRef54]

This is your lucky day,,,,,Aren't you glad you are using DESTROYER to get blasted before it happens on the DAT ??? It is best to make errors like this in practice...and DESTROY the real exam. No...Br is Priority group number 1.. BUT......the R group above you has a C with a Cl......making in group priority #2...COOH is # 3....Tricky indeed. LOOK CLOSER...you missed it. REDO THIS PROBLEM !!!!!!!

Hope this helps.

Dr. Romano

Thanks Dr. Romano!

 

[Allstarzallstarz]

Hi! I had a question on Question 57 in General Chem 2015 Version.

The answer states that if a strong base or strong acid is in excess that it cannot be a buffer. In Choice E, wouldn't NH4Cl be in excess as well, thus not allowing it to produce a buffered solution either? Nh4Cl is a strong acid correct?

 

[mOlar1!]

I had a question on #222 in ochem 2014 version. I don't understand why did we add the nitro group on the meta carbon and not para.

 

[nossdt]

Bio 532:

How do we know that the man's wife who is phenotypically "normal" doesn't happen to be a carrier?

 

[DAT Destroyer]

Bio 532:

How do we know that the man's wife who is phenotypically "normal" doesn't happen to be a carrier?

By "Normal" here, we mean Genotypicaly Normal. The question would have said a 'Carrier" if it meant a carrier.
On certain questions on the DAT, they must be clear.

Hope this helps.

 

[DentalNucleicAcid]

Hi Dr. Romano,

I have another question about math, from the 2016 math destroyer. It's number 27 of practice test 1. It says that 50% of a population are vegetarian and 35% ride bicycles, and 20% are both vegetarian and ride bicycles. And we need to know what the probability is that someone chosen from the population will be either vegetarian or a bicycle rider. I understand that 50% - 20% represents the vegetarians that don't ride bikes, and 35% - 20% represents the bike riders that aren't vegetarian. And so I'd think that this would lead us to say that 30% + 15% = 45% of the population either rides a bike or is vegetarian. But the solution also includes the 20% that are both vegetarians and ride bikes in the probability to give 65%. But these 20% do both of these things, not either or which is what the question is asking, so I'm confused as to why we included the 20%.

 

[WheatLom]

Hi Dr. Romano,

I have another question about math, from the 2016 math destroyer. It's number 27 of practice test 1. It says that 50% of a population are vegetarian and 35% ride bicycles, and 20% are both vegetarian and ride bicycles. And we need to know what the probability is that someone chosen from the population will be either vegetarian or a bicycle rider. I understand that 50% - 20% represents the vegetarians that don't ride bikes, and 35% - 20% represents the bike riders that aren't vegetarian. And so I'd think that this would lead us to say that 30% + 15% = 45% of the population either rides a bike or is vegetarian. But the solution also includes the 20% that are both vegetarians and ride bikes in the probability to give 65%. But these 20% do both of these things, not either or which is what the question is asking, so I'm confused as to why we included the 20%.

The question does not ask if they only are vegetarian or are only bike riders. Someone who does both is vegetarian and a bike rider.

50-20 is the only vegetarian and 35-20 is the only bike riders. but 20 also do both therefore 65% of the population will be either a vegetarian or a bike rider.

if you added them all from the beginning you would be including those who do both 3 times! and the answer would be 105% which can't be true.


If the question asked "What percent of the population is either vegetarian or rides a bike, but not both. then it would be 45% as you would not include those who do both.

 

[DentalNucleicAcid]

The question does not ask if they only are vegetarian or are only bike riders. Someone who does both is vegetarian and a bike rider.

50-20 is the only vegetarian and 35-20 is the only bike riders. but 20 also do both therefore 65% of the population will be either a vegetarian or a bike rider.

if you added them all from the beginning you would be including those who do both 3 times! and the answer would be 105% which can't be true.


If the question asked "What percent of the population is either vegetarian or rides a bike, but not both. then it would be 45% as you would not include those who do both.

Ohh so "either" in this case means that they have to at least do one of those things, but they could also do both..that wording is kind of tricky. I would usually think either means only 1 or the other. Thank you for clarifying!

 

[WheatLom]

Ohh so "either" in this case means that they have to at least do one of those things, but they could also do both..that wording is kind of tricky. I would usually think either means only 1 or the other. Thank you for clarifying!

**disregard the grammar ha**

Well lets look at it this way. out of 100 people 30 people swim and 45 eat chocolate 15 people swim and eat chocolate.


Overall 30 people Swim right. Seems simple. The same logic applies to 45 people eat chocolate. (I basically restated the given information).

The 15 people that do both are included in those totals they just happen to fit into 2 categories. So if they asked who eats chocolate. The people who do both are included, because even though they swim they still eat chocolate.
------------------------
When they ask who does either, but not both. Well the people who do both do not satisfy this requirement. There are not exclusive to one activity.

Lets say I ate chocolate and my friend swims, but you do both. We go to a pool that has 2 entrances that only lets people who fit the entrance criteria into the pool.

Line 1 - only Swimers
Line 2- only chocolate eaters

there is a line for either swimmers or chocolate eaters, but not both..

If we go to the same pool but has the same lines but are different criteria.

Line 1 - swimmers
line 2- chocolate eaters

there is a line for either swimmers or chocolate eaters, those who do both can go in either line.

 

[DentalNucleicAcid]

**disregard the grammar ha**

Well lets look at it this way. out of 100 people 30 people swim and 45 eat chocolate 15 people swim and eat chocolate.


Overall 30 people Swim right. Seems simple. The same logic applies to 45 people eat chocolate. (I basically restated the given information).

The 15 people that do both are included in those totals they just happen to fit into 2 categories. So if they asked who eats chocolate. The people who do both are included, because even though they swim they still eat chocolate.
------------------------
When they ask who does either, but not both. Well the people who do both do not satisfy this requirement. There are not exclusive to one activity.

Lets say I ate chocolate and my friend swims, but you do both. We go to a pool that has 2 entrances that only lets people who fit the entrance criteria into the pool.

Line 1 - only Swimers
Line 2- only chocolate eaters

there is a line for either swimmers or chocolate eaters, but not both..

If we go to the same pool but has the same lines but are different criteria.

Line 1 - swimmers
line 2- chocolate eaters

there is a line for either swimmers or chocolate eaters, those who do both can go in either line.

Wow that's a very thorough explanation, I appreciate it, thanks!

 

[dentalpredent2016]

Is there a more detailed answer to #65 on gchem destroyer 2016? Why can't Al2O3 be the answer?

 

[DAT Destroyer]

Is there a more detailed answer to #65 on gchem destroyer 2016? Why can't Al2O3 be the answer?

A detailed solution was not needed. An ionic compound does NOT exist as a discreet molecule. This is stated in another problem as well.

Hope this helps.

Dr. Romano

 

[kimball]

is this the correct trend for carbocation stability:

3 Benzyllic/ Allilyc > 2 benzylic/allylic = 3 carbocation > 1 benzylic/allylic = 2 carbocation > 2nd vinylic = 1 carbocation > 1 vinylic = methyl

or is 2 benzylic equivalent to a tertiary carbocation?

 

[DAT Destroyer]

is this the correct trend for carbocation stability:

3 Benzyllic/ Allilyc > 2 benzylic/allylic = 3 carbocation > 1 benzylic/allylic = 2 carbocation > 2nd vinylic = 1 carbocation > 1 vinylic = methyl

or is 2 benzylic equivalent to a tertiary carbocation?

You have a good idea of general stability. Sometimes,,,,,,it is difficult to exactly get a correct order......on the experimental level. Not much would beat a tertiary carbocation.......but as you stated,,,,,tertiary benzylic and allylic certainly would since resonance is a contributing stability factor. I would also agree that a secondary benzylic and allylic would be very very close to that of a tertiary carbocation. Most advanced Organic Chemistry texts such as the Michael B. Smith and Francis Carey texts give you actual values.....which would concur with your estimates. For the DAT exam......make sure that you know that a tertiary would be the best.,,,,,,unless trumped by a secondary or tertiary allylic/benzylic system.....or an acylium ion of the structure RCO+.

Hope this helps..

Dr. Romano

 

[zyzzbruh]

I'm extremely confused on an elementary topic, please help
Triple bonds>double bonds>single bonds in terms of vibration frequency
If they are all single bonds, the lightest pair of atoms has the highest vibration frequency?

--also, if triple bonds vibrate with a higher frequency, why do sigma antibonding orbitals have a higher energy than antibonding pi orbitals?

 

[Charles_Darwin]

I'm extremely confused on an elementary topic, please help
Triple bonds>double bonds>single bonds in terms of vibration frequency
If they are all single bonds, the lightest pair of atoms has the highest vibration frequency?

--also, if triple bonds vibrate with a higher frequency, why do sigma antibonding orbitals have a higher energy than antibonding pi orbitals?

The stiffer the bond and the lighter the atom, the higher the frequency.

Sigma orbitals have more energy than pi orbitals. Triple bonds have a sigma orbital and two pi orbitals - this is stronger than a single bond with just a sigma orbital.