When assigning priority dealing with double and triple bond equivalences,
which of these would be higher priority: a carbon with an OH group, or a carbon
with a nitrile group?
The carbon with the OH group has higher priority, because oxygen has a higher atomic number than nitrogen.
#4 from exam 1b its a newman projection. Can you
have more then one global max and it looks to me that
there really isn't just one anti-confermer?
You can indeed have more than one global max and this compound does have more than one. It's also tough to "name" one conformer the anti conformer when you have two substituents on one of the carbons involved in the Newman projection.
Do you show stereochemistry when there is only one
substituent such as #3 the 2nd one on exam 3b?
Hmm. Looks like there are two substituents on the second reaction on number 3 on test 3b.
The product will have Br instead of the OH, with an inversion of stereochemistry at the reactive carbon. In other words, the product will be cis rather than trans.
I 'm having trouble with syn periplanar? How can
you tell? Is it just the methyl group moves? What type
of problem could we encounter on the exam?
Syn periplanar is very rare. It's likely you'll never see it. It doesn't involve any methyl group moving. (Are you talking about rearrangements?)
I am having a bit of a problem remembering what the
differences are between sec-butyl and iso-butyl. I am
just trying to draw molecules and those are two of the
substituents that I need to draw.
Here are the structures for cyclohexane with isobutyl and sec-butyl substituents.
You should notice that the sec butyl group is a four carbon chain and the chain is attached at the second position. Isobutyl, on the other hand, is a branched chain. It's attached on one of the chains rather than in the middle.
I was working on the Electronic Flash Cards web site
and was wondering if there were any reaction divisions
that we would not be held accountable for--many of the
lower "options" on the site I know we've not covered, but
I just wanted to make sure that I was working on those
that we could do...
You should only worry about the ones under acids/bases, alkanes, alkenes, and alkynes. Strangely enough, they classify alkyl halides under alkanes.
I understand the resonance structures and the hybrid
of the carbocation, I think. But I was doing the
questions in chapter 14 and I don't understand how to do
numbers 3 and 4. I looked at the solutions after I had
solved it myself, but only one of my drawings
corresponded to theirs. I don't understand how they got
those answers from the resonance structures. Could you do
a step by step diagram with arrows to show the
The first step in the reaction of HCl with 1,3-pentadiene is reaction with one of the two double bonds. Here's one of the two possible reactions, with both resonance forms of the ion shown:
The Cl can come on from either place that has a positive charge. You should try showing the reaction from the double bond on the left and then drawing the other resonance form. That should give you all four products.
Okay, here goes on problem 14.4. What do you notice about the carbocations that I drew compared to the ones that you drew? I'm hoping you'll think about them as primary, secondary, or tertiary. If one resonance hybrid has at least one contributor which is more substituted, that resonance hybrid will be favored. So you would get a larger fraction of the products from that resonance form.
What is the difference between a hydride shift and
A hydride shift is one type of rearrangement. The other type is a methyl shift or an alkyl shift.
I've been working through the old tests to try and
determine which of my skills (or, as is obvious with some
of these tests non-skills) I need to work on. I was
wondering if you either 1) had or 2)knew of where I could
gain access to mind-numbing amounts of reaction problems.
I guess I'm looking for a sort of "spectral zoo" of
reactions: problems of reactants and products where I need
to determine the reagents/catalysts, etc. or of just
determining the product from having the first two parts of
the reaction. I've already scanned through the ones in
the book, and was just wondering if you had any that were
more of the style that you give in class. If you have any
recommendations I'd love to know :) :)
Check out the links listed under Useful Resources. The last several sound like just what you're looking for.
What do we have to know about 1,2 diol cleavage? Can you give an
example reaction and/or mechanism?
You don't need to know anything about 1,2-diol cleavage. I think it uses IO4 as the reagent, but I couldn't tell you a mechanism and I don't expect you to tell me one. If you decide to be a carbohydrate chemist for your career, you may need to know this reaction. Otherwise it's not a very important one as far as I'm concerned.
What would be some possible application questions from chapters
7,8,14 that might appear on the final? I consider application problems
the problems that are not just show the product from this starting
material and reagent.
Chapter 14 application problems would be synthesis questions for Diels Alder and explanation questions for 1,2 vs 1,4 addition to conjugated dienes. I might ask a multiple choice question about conjugated dienes and partial double bonds on the single bond positions.
Chapter 7 is about alkenes and chapter 8 is alkynes. I could envision asking synthesis questions that would involve these chapters. I also like the questions that ask why something wouldn't happen as shown or mechanism type questions, either a full blown mechanism or an explanation question that requires some mechanistic understanding.
Are we going to need to be able to name any type of
alkynes? If so, can you give some examples of some of the
tougher ones to name?
No, I won't ask you any nomenclature questions with alkynes. The most I might do is ask you an explanation or synthesis question about an alkyne and give you its name instead of its structure. I would do that with acetylene (HCCH) or a simple alkyne like 1-pentyne or 4-octyne.
Can you bring some example spectra problems to work in the review
session tomorrow? Is that book with spectra problems still on reserve
in the library?
The book with spectral problems is still on reserve in the library. I will try to bring the computer on the cart so that we can do as many spectral problems as you like.
I was looking at notes and the book trying to get a better grip on the Sn1
Sn2, E2, E1 stuff and because i was looking at the book when i recopied my
notes, i changed a lot of things you said in class. Mostly the stuff about
what a strong, weak , or really weak base is.
If you have an oxygen with a negative charge on it, it's probably a strong base. That generalization works for hydroxide (-OH) and alkoxides (-OR or RO-). If the carbon with the oxygen also has another oxygen (double bonded), then it's a weak base (like acetate, OAc or CH3CO2-). Strong bases include ethoxide (EtO- or CH3CH2O- or -OEt), butoxide, any old alkyl group with an oxygen and a negative charge. Sometimes the negative charge hides behind a metal like Na or K or Li. Alcohols (ROH or HOR) are NOT strong bases--they are weak bases, much weaker than ammonia (which you probably remember from CHE 11 and 23).
Anyway, i'm just working on the chapter 14 problems and i am on 21 c (the
first one) and i don't understand why only one product is made? why doesn't
the Cl go the 4th carbon also?
The reason only one product is formed is that the other product is exactly the same as the first one. Go ahead and draw out the product from the Cl adding at the 4th carbon and compare it to the other product. If you named them, they would be the same due to the molecule's symmetry.
Also, i was wondering if the final was going to be more weighted towards the
new material that we have not had on a test or if there were other areas
that are going to be more stressed.
The exam will NOT be weighted more heavily toward the new material that you haven't been tested over. The coverage will be equally spread through the whole semester. That's handy, since now you probably think nomenclature is very easy.