Bases and Nucleophiles

Hi Alex,

I am still confused on the difference between a strong base and a strong nucleophile. . . 

A strong base = a strong nucleophile

We added in class "if it's not acting as a base" and I'm not sure what this means exactly.  

Thanks,

Confused person....
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We added in this qualifier because it helps us distinguish between Sn2 and E2 reactions.  In an Sn2 reaction, we'll be using a nucleophile; in E2, we'll be using a base.  A strong nucleophile is a strong base... but we'll only see nucleophiles in Sn2 reactions.  So if the species is acting as a base, it's actually E2.

Hope this helps!

Re-Cap of MSCT I

Hey everyone!

After each session we have together, I will be sending out a re-cap email.  The purpose of this email is to give you some pointers on what you should have gotten out of that session, tips and tricks on how to work with the content, and advice of other resources to check out.  It took me a long time to put these emails together, so please go through and read them!  They're chock-full of good stuff.

Although we didn’t review any hard science in our first class, we’re aware that all of the information presented may have been overwhelming.  Thus, the primary purpose of this email is to briefly review the main points presented in MSCT I. 

We opened the lesson with a brief discussion of where the MCAT fits into the admissions process.  The MCAT is combined with your undergraduate GPA to predict your future performance in medical school.  A study by the AAMC concludes that the MCAT “essentially replace[s] the need for uGPAs in their impressive prediction of Step scores,” so the bottom line is that the MCAT is a critical component of the medical school admissions process!  The MCAT’s success is due to its design as a critical thinking exam, not as a content-driven exam.  Basically, the MCAT is kind of a big deal, much like Ron Burgundy. 

The key point is to not be scared by all of this!  The MCAT is not an obstacle, but an opportunity:  it’s an opportunity to demonstrate that you are disciplined and determined to do what it takes to succeed on the MCAT, thus allowing medical schools to think that you will be disciplined and determined enough to become a great physician!  Procrastination is the scourge of many MCAT students, thus we devoted some time discussing how to use positive thinking to avoid that potential problem.  You’ll receive an email later that revisits that discussion in greater depth.

During the lesson we also discussed how to use the Kaplan resources.  Please see the attached document titled “Kaplan’s MCAT Classroom Resources” for a thorough review of that conversation.  The other PDF document, “Navigating KapTest”, answers some of the frequently asked questions we have received about where to find the homework assignments for a particular session, and how to access the explanations to the online quizzes and exams.

Your Required Homework before Physics 1 is as follows:

• Read Physics Review Notes, chapters 1-3.

For those of you who haven’t had physics in a while, or would like to brush up on your math, I recommend you do the following:

• Physics Foundation Review Unit 1
• Math Foundation Review
• This covers trigonometry, geometry, exponents and logarithms.  You are likely to see these concepts on the MCAT, so make sure you’re really set on them!

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

Helpful Hints:

• Don't forget about the class journal!  You can post questions on absolutely anything there, and I'll do my best to respond back within 24 hours.  You can access the journal at mchv10702.blogspot.com.  The username is mchv10702, and the password is letsgo45T.  I'll also post the class-wide email to the journal after each session.
• Begin to familiarize yourself with ALL of the Kaplan MCAT resources, most of which can be found through your online syllabus.  We know that the vast amount of different study materials can be intimidating at first, but they have been designed to address the different stages of test preparation.   Take that first step by reading through the links under “Getting Started.”
• Register NOW for your test date if you haven’t already (www.aamc.org/mcat).  You’d be amazed how quickly the Prometric centers fill up in major cities with lots of colleges.  When I was taking my MCAT course in Philadelphia, another student in my class had to travel all the way to Montreal, Québec just to take her MCAT.  You don’t want that added stress on Test Day.
• Be sure to prep your flashcards (i.e. take them out of the plastic wrapping) and separate them into three priorities.  First priority includes content areas in which you have weakness—these you should begin reviewing now.  Second priority includes content that you understand but have not seen in a while and so need to refresh.  Third priority includes content in which you are strong and can defer for later review.
• Speaking of flashcards, make sure to begin making your own flashcards for the formulas you see in the Review Notes.  The formulas in these first three chapters will – I promise you – be tested on the MCAT.  The sooner you know and understand these formulas, the better.
• This one is really important:  develop a long-range and short-range study plan!
• If you don’t have one, get a calendar and write in all of your non-MCAT commitments:  exam dates, paper due dates, personal appointments, and other important events (e.g. religious holidays, birthday parties, etc.).
• Next, add in each class for our MCAT course (once inside the KapTest syllabus, click on the “My Attendance” to view the schedule), and jot down the associated preview assignments for each session.
• Once you have a lay of the land, you can begin to plan ahead for difficult spots in your schedule.  In terms of our MCAT course, you will want to keep an eye out for the Unit II sessions (i.e. Physics II, General Chemistry II, etc.).  These sessions cover a rather large volume of content.  For example, the preview assignment for Physics I only consists of one online workshop and three chapters.  The preview assignment for Physics II consists of three online workshops and five chapters.  And it isn’t exactly easy stuff either.  In short, you want to map out every commitment between now and your Test Day so that you can plan ahead of time how to ensure you can meet all of your obligations.
• After you have an understanding of your long-term obligations, you can develop a short-range to-do list that specifies what task you must do on each day over the next week, and what tasks you want to do on each day over the next week.  Always ensure you prioritize your academic studies over all other commitments – including MCAT preparation.  All graduate schools desire applicants who have demonstrated academic excellence.  The MCAT is offered over twenty-five times per year, thus there’s flexibility for you to push back your test date if needed.  That said, gain control of your schedule now so that you can get the best of both worlds!

Finally, I would like to close by reminding you that my role, as your instructor, is to function as your guide to preparing for the MCAT.  Therefore, if you have problems with your online resources, have questions about the course, or develop concerns about the classroom, do not hesitate to contact me immediately.  Kaplan leads students to Test Day success by offering them excellent teaching, cutting-edge resources and personalized mentoring.  I want to hear from you about what we are doing well, and what we can be doing better.

Orgo ch2 #8

I'm having trouble understanding:

O.Chem chpt. 2

Problem 8

The solution states that the answer is B because the methyl groups will not be competing for the space of the hydrogens, however, I thought B would be incorrect since the methyl groups are so close to each other, it would cause steric strain
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Good question!  While the methyl groups are relatively close to each other, we won't have too much steric strain here.  If you create a Newman projection down the bond between the two methyl groups, you'll see that they are actually gauche staggered.  While this creates a bit of strain, it's still pretty small.

If you look at the other answer choices, C has a LOT of strain.  The boat form of cyclohexane is quite unstable because of a large amount of nonbonded strain between the substituents on the carbons at the "points" of the boat.  For A, while there is not much torsional strain, there is a lot of nonbonded strain with the other axial components of the cyclohexane.

In general, when you're looking at cyclohexane, equatorial is ALWAYS preferable.  Since B gives us two methyl groups in the equatorial position, it's gotta be the most stable.

Physics Foundation q 10

Two people are pushing on a box of mass 80 kg. One person applies a force of 100 N, and
the other applies a force of 200 N in the same direction. A frictional force of magnitude 80
N acts in the opposite direction. What is the acceleration of the box?
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As with any dynamics question, we'll use a three-step method:
1.  Free-body diagram
2.  Newton's second law
3.  Solve for what we need

The free body diagram here should have our box with all the forces labeled.  For consistency's sake, I'll call right positive, and up positive.  The forces we have are:
-Gravity, which is equal to mg = 80 kg(10 m/s²) = 80 N [downwards]
-Two applied forces, both acting towards the right, equal to 100 N and 200 N.
-Friction, equal to 80 N.  Since friction will ALWAYS oppose motion, we should know that it would be oriented towards the left, even if they didn’t tell us that in the question stem.
-Normal force, equal to 80 N.  The normal will be perpendicular to the surface between the objects, and here, that means it's oriented upwards.

Our second step will be Newton's second law, F = ma.
There's no acceleration in the up/down direction, so we'll ignore Newton's second law in that dimension.  However, there is acceleration left/right.  So let's set up Newton's second law:
Fnet = ma.
If right is positive, then our forces that direction are +100N and +200 N.  Friction is to the left, so it's -80N.
Fnet is then 100N + 200N - 80N = 220N.  Our mass is 80 kg, so we can rewrite Newton's second law as:
220N = 80kg (a).  Solving for a (our third step), we get 220N/80kg = 2.75 m/s²
Hope this helps!

Welcome to Club MCAT!

Please post your questions here so we can keep moving forward towards "45T"s together. Best of luck as you continue your prep for the January test dates!