2009 ADA DAT test error questions

[Stacker]

How many isomeric mono-substitution products are possible for the bromination of the aromatic hydrocarbon naphthalene?
1, 2, 3, 4, or 5. I said 4 because there are two chiral centers. 2^n = 2^2 = 4 different structures. But ADA says 4 is wrong. Why is it wrong?

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[Stacker]

 

[Stacker]

The heat of formation reaction for solid CaCO3 is

Ca(OH)2(aq) + 2H2CO3(aq) → CaCO3(s) + H2O(l),
CaO(s) + CO2(g) → CaCO3(s),
Ca2+(aq) + CO32–(aq) → CaCO3(s),
or
2CaCO3(s) →2Ca(s) + 2C(graphite) + 2O3(g)

 

[jbinna]

How many isomeric mono-substitution products are possible for the bromination of the aromatic hydrocarbon naphthalene?
1, 2, 3, 4, or 5. I said 4 because there are two chiral centers. 2^n = 2^2 = 4 different structures. But ADA says 4 is wrong. Why is it wrong?

I believe it's because one of them will be a "meso" which is achiral. So it should be 3, not 4.

 

[drill-and-fill]

wouldn't it be 2? Seems very similar to DAT Destroyer Orgo question #2.

 

[MuskieMan33]

wouldn't it be 2? Seems very similar to DAT Destroyer Orgo question #2.

That is what I was thinking too. The two carbons are equivalent because they have the exact same groups. So say the top of the two chiral carbons could be brominated (2 positions), flip it 180 degrees vertically (after it has been brominated in your head) and its the same thing on the same carbon.

The two on the left are the same and the two on the right are the same. Hope this makes sense!

 

[Stacker]

That is what I was thinking too. The two carbons are equivalent because they have the exact same groups. So say the top of the two chiral carbons could be brominated (2 positions), flip it 180 degrees vertically (after it has been brominated in your head) and its the same thing on the same carbon.

The two on the left are the same and the two on the right are the same. Hope this makes sense!

You can't brominate that center carbon between the two benzenes. I'm saying that the two carbons that are able to be brominated are brominated in such a way that two forms will be the products: R and S.

 

[jbinna]

wouldn't it be 2? Seems very similar to DAT Destroyer Orgo question #2.

I misunderstood, koreano is right. The answer is 2, here are the examples from Destroyer.

 

[MuskieMan33]

I misunderstood, koreano is right. The answer is 2, here are the examples from Destroyer.

Crap, your right! lol. I could have sworn I saw a mono addition problem very similar to this in destroyer, except a halide was added to the more substituted carbon.
You said #2, but I think i had #110 in mind, with a conjugated diene (not naphthalene) and 1,2 addition of Cl would be the major product (on the carbon that the two rings share). I'm glad you caught that. Now I know a few more things that I need to polish up on before the DAT.

(In the picture I didn't erase one of the double bonds) like I should have. I'm glad you pointed out my error. I'm going to go ahead and delete that so I don't look like an idiot.
Now I'm going to be more careful about the conjugated dienes and bicyclic compounds! Thanks!

But I now I feel like there are more than just 2 monobrominated compounds you can get. I'm going to have to draw a few things out first. I'll be back! lol.

 

[ScarletKnight24]

The heat of formation reaction for solid CaCO3 is

Ca(OH)2(aq) + 2H2CO3(aq) → CaCO3(s) + H2O(l),
CaO(s) + CO2(g) → CaCO3(s),
Ca2+(aq) + CO32–(aq) → CaCO3(s),
or
2CaCO3(s) →2Ca(s) + 2C(graphite) + 2O3(g)

second one.

 

[ScarletKnight24]

How many isomeric mono-substitution products are possible for the bromination of the aromatic hydrocarbon naphthalene?
1, 2, 3, 4, or 5. I said 4 because there are two chiral centers. 2^n = 2^2 = 4 different structures. But ADA says 4 is wrong. Why is it wrong?

Where are the two chiral centers?

 

[Kingsta2426]

Where are the two chiral centers?

I don't think there is any.

Correct. There are no chiral centers because all Carbons are SP2 hybridized.

 

[Kingsta2426]

The heat of formation reaction for solid CaCO3 is

Ca(OH)2(aq) + 2H2CO3(aq) → CaCO3(s) + H2O(l),
CaO(s) + CO2(g) → CaCO3(s),
Ca2+(aq) + CO32–(aq) → CaCO3(s),
or
2CaCO3(s) →2Ca(s) + 2C(graphite) + 2O3(g)

It would be the reverse reaction of the last one if it only formed 1 mole of CaCO3 because a formation reactions uses reactants in their elemental form (O2 gas, C graphite, Na solid, ect) and can only form 1 mole of product. So I think this question is an error.

 

[ScarletKnight24]

It would be the reverse reaction of the last one if it only formed 1 mole of CaCO3 because a formation reactions uses reactants in their elemental form (O2 gas, C graphite, Na solid, ect) and can only form 1 mole of product. So I think this question is an error.

Your explanation is right but the last one its O3 not O2(g)

also my previous post is also wrong since none of the reactants are in their standard elemental state.

 

[Stacker]

Too late. Took the DAT. Got a OC=20...