Re-Cap of Organic Chemistry I

Hey everyone!

First, let me answer some of the questions that came up during our last session:

Does a higher boiling point usually correspond to a lower freezing point?  There really doesn’t seem to be a strong correlation here, or at least not one that’s strong enough to depend on for Test Day.  I looked up the boiling and melting points of some common solvents (http://en.wikipedia.org/wiki/List_of_boiling_and_freezing_information_of_solvents) and you can see there isn’t a great correlation.

Can angle strain exist in a non-cyclic molecule?  Not for anything you’d see on the MCAT.  Some complicated molecules (particularly those that involve large bulky groups) can create so much non-bonded strain, that the angles within the molecule become distorted.  That being said, you’re really only going to see angle strain in the context of cyclic molecules on Test Day.  Remember that cyclopentane and cyclohexane have very low angle strain, because they adhere to an angle close to 109.5°.

Is there any difference between the different listings for the same test site on the AAMC website?  There is not.  They’re all equally fine, and would enroll you for the same test at the same location.

How many seats are at the

601 Walnut Street

MCAT location?  I tried calling them earlier today and haven’t yet gotten through.  I’ll try again on Monday, and can hopefully give you all an answer on Tuesday.

As a reminder, if you have not yet checked out the class blog, here is the sign-in information one more time:

mchv10702.blogspot.com

username:  mchv10702

password:  letsgo45T

All of the past emails have been uploaded to the class journal, so if you did not receive any of them, you can find them there!

Starting with our next session, we will be hitting a tough stretch in our schedule where an awfully large volume of science will be covered within two weeks.  Thus, let me remind you again that is in your best interest to carefully plan out your schedule through the remainder of this month to reduce the probability of falling behind.  As usual, we’ll discuss your preview and review assignments:

Your required homework for our upcoming Biology I session:

• Biology Review Notes:  Chapters 1-5 and 14
• OWQ:  Generalized Eukaryotic Cell
• OWQ:  Microbiology

o   General Comments: the material reviewed in the review notes and the OWQs contains a lot of detail, but it’s way too early in your prep for the MCAT to concern yourself with memorizing details.  For now, stick to the main concepts taking note of key contrasts (prokaryotes vs. eukaryotes, different organelles, lytic vs. lysogenic) and concepts that are easily applied to problem-solving questions (i.e. enzymes and genetics!).

For those of you who would like some additional Biology review before class, I recommend the following:

• Biology Foundation Review Unit 1

To reinforce what we have covered in Organic Chemistry I, complete the following:

• Organic Chemistry Subject Tests 1, 2 & 3
• Hydrocarbons Test 1
• Molecular Structure of Organic Compounds Test 1

All of these items are available on your syllabus through www.kaptest.com.

Helpful Hints:

• Remember that MCAT Organic Chemistry is NOT like your undergraduate Organic Chemistry classes.  Success on the MCAT does NOT require unending memorization of organic chemistry reactions, but rather a strong understanding of concepts which you then apply to reactions that you may have never seen before.  These concepts include:
• What makes a good nucleophile?
• What makes a good electrophile?
• What makes a good leaving group?
• What makes a good oxidizing or reducing agent?
• How do the different functional groups respond to oxidizing or reducing agents?
• What creates or lowers stability in a molecule?
• What affects the reactivity of a given molecule?
• Isomerism can arise from only two differences:  bond connectivity OR spatial arrangement.  Remember that the most heavily tested isomers on the MCAT are enantiomers and diastereomers.  Key to this difference is that enantiomers have the same physical and chemical properties except for two things:  reactions in a chiral environment, and rotation of plane-polarized light.  Diastereomers, on the other hand, have the same chemical properties but differ in physical properties like solubility, melting point and boiling point.
• Keep things in perspective – Organic Chemistry is only about 25% of the Biological Sciences section!

With respect to our Organic Chemistry I session, there are a few topical tests listed in the review assignments but most of the concepts we reviewed in Organic Chemistry I are not tested directly on the MCAT.  As noted earlier, these concepts serve as the foundation upon which we can understand reaction mechanisms we will cover in subsequent organic chemistry sessions.  The key concepts to be familiar with from Organic Chemistry I are outlined below:

·         Know the functional groups and the relevant nomenclature prefixes and suffixes

·         Understand the differences between different classes of isomers (structural versus stereoisomer, conformational versus optical, diastereomer versus enantiomer).

o   Fundamentals: how to assign axial versus equatorial for cyclohexane, how to assign R and S stereochemistry for chiral compound, how to name with E and Z.

o   Key concept: how to resolve an enantiomeric mixture (passage II).

·         Reaction Mechanisms of Alkanes: S_N1/S_N2/E1/E2

o   Knowing the mechanism, kinetics, sterics, nucleophile/base strength, solvent, and stereochemistry for each is nice, but…

• UNDERSTANDING the why behind the trends is really the key point.  Look at the table at the end of the lesson and be able to explain each entry in the table – for example, why is S_N2 favored when you use a good nucleophile on a primary substrate?
• The four key factors that help distinguish which reaction occurs include:  substitution at the substrate carbon, presence of a good nucleophile and/or base, solvent and presence or absence of heat as a catalyst.

Well, that’s it for now.   See you next time!