Need help with some questions on the DAT sample test (orgo section)

[rickblas]

---

Members do not see this ad.

hey! (new to these forums) so I just started seriously studying for the DAT; moreover, I have been casually reviewing for a couple of weeks so far (test date: June 29th!) and was doing some problems and i did the DAT sample test (the one free on the ADA website). I took the Full science section timed and according to the scaling I didn't do as bad as I thought! I got a ~20 in bio (I need to learn physiology...never took it) a 27~ in GC (only one wrong!) and a ~19 in orgo. Also, as a side note, is this sample test reflective on how the real DAT is because I thought it was really managable. Anyway, after reading the answers I knew, for the most part, why the correct answer was correct and why my wrong answers were wrong except for a few questions:


#74 Organic section:
How does the energy content of the transition state of a chemical rection compare with that of the reactants and the products?

Correct answer: It is greater than both reactants and products.

**Why is this??? Is it because the transition state isn't stable and has more energy??? helP!😕

#76 The reaction of benzoic acid with HNO3/H2SO4 will give? (I understood that it will add a NO2 group to the meta because CO2H on the ring is electron withdrawing but...)

Correct answer: Nitrobenzoic Acid with nitro grp attached to beta AND will be faster than nitration of benzene. **WHY is it faster????😕

Any help is appreciated! Also...another side note... I have never heard of Cliff's AP bio but i read among these forums that it is a "must" for review of biology so I was going to buy it but wasn't sure which one it is. Is this one the correct Cliffs AP Bio? http://cgi.ebay.com/Cliffs-Ap-Biolo...m&pt=US_Texbook_Education&hash=item439f8daa64

THANKS! Any help is appreciated

 

[UndergradGuy7]

That sample exam is much easier than the real thing. It has been mentioned here before. Yes, that is the Cliff's ap biology book everyone is talking about.

A transition state, is a highly unstable stage. It is high in energy (it is unstable) so it is higher in energy than reactants and products.

Not sure about the rate thing.

 

[lala05]

#76 The reaction of benzoic acid with HNO3/H2SO4 will give? (I understood that it will add a NO2 group to the meta because CO2H on the ring is electron withdrawing but...)

Correct answer: Nitrobenzoic Acid with nitro grp attached to beta AND will be faster than nitration of benzene. **WHY is it faster????

Check the answer sheet again... the answer states that the reaction will give meta-nitrobenzoic acid "and will be slower than nitration of benzene." So you were right... both substituents (COOH and NO2) are electron withdrawing, which will deactivate the ring and make the rate of electrophilic aromatic substitution reactions, including nitration, much slower than that of benzene.

 

[rickblas]

Wow...I completely read that wrong; I guess i was right 🙄.

Thanks guys!