1) do you know which bonds will vibrate at the highest frequency? for example, triple bonds, double bonds, conjugate molecules...

2) are alcohols soluble in water? some books say yes and some books say no.. i was just wondering. i know the -OH group can hydogen bond with water molecules but what if the chain is too long? does the no polarity of the linear chain overcome this H-bonding, ultimately making it insoluble?

3) for those who took the DAT already, do we have to remember IR wavelengths or NMR numbers? would questions directly ask, what gives a 1000 cm-1 or what is this that is 5.3 downfield?

4) i'm a little confused on how aprotic or protic polar solvents affect SN1 vs SN2 Rxns. which goes with which? i'm reading kaplan and ap cliff's. they both have reverse answers. i was wondering, which one stabilizes the carbocation and which is used for the SN2. My other questions is about E1 vs E2 rxns. Which goes with bulky bases or non-bulky. where would the double bond go to? i don't understand zeitsiv's(sp?) rule on which becomes more stable.

sorry for the long questions. good luck to all studying.

1) Conjugation (in carbonyls) lowers absorption frequency. Triple bonds absorb high then double bonds (I think alkynes are ~2200 while alkenes are just past 1600). Alcohols, amines, amides, and terminal alkynes all absorb at very high frequencies.

2) Alcohols (of relatively low m.w.) are miscible in water meaning they are infinitely soluable, add enough and the alcohol becomes the solvent while the water becomes the solute. As molecular weight increases though solubility does decrease, I don't remember the cut-off though.

3) Know overall concepts, you could be given a molecule and asked to predict the splitting pattern or be giving an NMR and asked to identify the molecule...same with IR. You don't need to know every detail but knowing where a carb. acid absorbs or where a proton on an aromatic shows up should be pretty much commonsense. Also, be familiar with carbon NMR

4) Bulky bases (or bulky substrates) almost universally favor SN1 and E1, backside attack and inversion is too difficult with the steric hindrance so a carbocation is the only way to proceed. Remember though since you are dealing with a carbocation that rearrangements are likely to produce the most stable ion. The double bond will go wherever it is most substituted. So for example if you dehydrogenate butane you will get 2-butene instead of 1-butene because the double bond will have a methyl substitute on both sides instead of just an ethyl substitute on one.

Polar protic solvents (water, alcohols) are used mainly for SN1. They help stabilize the cation formed and lower the activation energy. You want a less polar solvent for SN2. SN2 also uses polar aprotic solvents (remember the crown ethers) since they can strengthen an otherwise weak nucleophile (like fluorine).

If you're still having trouble I'd go back to your textbook and reread the section. Those reactions are very detail oriented and are tough to learn from a watered down book. If all else fails try your old professor, face to face help is much easier than learning over the computer.