Posts Tagged "organic chemistry"

Preparing for Organic Chemistry This Fall

Posted on August 5th, 2017

One of the questions we are repeatedly asked at StudyOrgo is “how do I to get ahead in organic chemistry this fall semester?” Many of you have heard that organic chemistry is a brutal class that does little but to depress your GPA. While it is true that this course is challenging, we here at StudyOrgo are devoted to helping you get the “A” you deserve!

Organic chemistry gets a bad name because it assumes that you are experts with regards to all of the general chemistry from freshman year, and you are now responsible to know it!  As an analogy, think of your chemistry courses as a pyramid to reaching your degree goals.  Organic chemistry is directly placed in the middle of the pyramid, it will be very important not only for the MCAT or DAT exams, but also for future advanced courses.  Organic chemistry is supported by General Chemistry, which is why you took it last year.  Fortunately, StudyOrgo is placed in the center of your pyramid base and we are here to help all of your organic chemistry questions.  Our simple and clear-cut explanations of reaction mechanisms and concepts will easily help you with anything you might struggle with this semester.  Here are a few tips on how to prepare today for the course this Fall.

chemistry pyramid

  • Open your text book –Read the title and abstract on the first page of each chapter and check out the number of pages. It will give you a very quick idea of what you will be learning about in each chapter and how much material you will be covering.
  • Look at a syllabus – Remember, your syllabus is an official contract between you and the professor. They must disclose what you are required to learn and how you will be graded. Professors can remove requirements but cannot easily add them. Use this to your advantage! Highlight the contents or reactions of the book that will be required and use this to focus your attention on while studying over the semester.
  • Schedule your studying! – Now that you know where the book is and a rough idea of what you are responsible for learning from the syllabus, take a calendar and divide the time you have to each test by the number of chapters. Schedule 2-3 hours a week to study and DON’T SKIP OR RESCHEDULE. Think of it as a doctor or dentist appointment – you just have to do it! Also, if you plan your studying ahead, you will be less likely to schedule something that gets in the way because you will already have penciled it in! Use your Smartphone calendar to send you alerts and reminders for your studying appointment.
  • Read ahead – If you have time this summer, read at least two chapters to get yourself ahead of the class. Don’t try to understand everything, just pay attention to the words used and the ideas. This will allow you to pay more attention and ask questions about the details in class instead of scrambling to write down notes and drawings.
  • Sign up with StudyOrgo – The Editors at StudyOrgo have spent numerous hours reviewing and preparing the material in the most crystal-clear and “get-to-the-point” manner as possible. We consult students and ask for their opinion on whether they understand the material as presented. We provide quick descriptions and in-depth mechanism explanations. Many of our reaction have multiple examples, so you can learn and then quiz yourself in our website! For the student on-the-go, we have also developed a mobile app (iOS and Android) provides all the functionality of the website! All of these benefits are included in your StudyOrgo membership!

With a little time management and help from StudyOrgo, you will have no trouble getting an “A” in Organic Chemistry this year!

How can I tell if a hydrogen is a wedge or a dash in a chair skeleton?

Posted on March 19th, 2017

 

“How can I tell if a hydrogen is a wedge or a dash in a chair skeleton?”

Here at StudyOrgo, we frequently get questions about topics in organic chemistry that are usually quickly covered, poorly described or expected that you know from previous courses.  These concepts are really important to understanding the more complex topics to come.  In this article, we will cover the concepts of stereochemistry descriptions using bold and wedged bonds.  This is just a preview of the detailed topics and materials available with your membership to StudyOrgo.com.  Sign up today!

The first thing we have to do is determine is how you want to orient you molecule.  Let’s take (1R, 2R) 1,2-dimethylcyclohexane for example.  If we orient the molecule to have the methyl groups on the right side, we see that we have two stereocenters available.  But the current drawing doesn’t indicate the stereochemistry yet.  That’s what the bold and hashed bonds will indicate.

Next, we have to visualize the cyclohexane ring in the chair conformation.  Remember, that the skeleton image shown above is more conveniently drawn, but loses the 3rd dimension information, so you have to put it back in the chair to determine which should be bolded and which should be wedge.

Next, we have to confirm that that the stereochemistry is correct.  To do this, you need to practice selecting most important substituents and rotating to assign stereochemistry.  Follow along with the examples below, using the blue and pink carbons shown.

At this point, you should be able to see how the hashed and bolded bonds are now appropriately drawn.  The pink stereocenter will be bolded, suggesting it is above the plane of the ring and the blue stereocenter will be hashed, suggesting it is below the plane.  Drawing the Newman Projection down the red bond shows that the methyl groups are “anti” to each other, making this a stable conformation.

 

 

Intermolecular Forces Review

Posted on September 5th, 2016

Studying ahead for Organic Chemistry this Fall semester is a good way for reaching and maintaining a great grade in this class.  Most students find the pace of this class very challenging compared to other courses.  This is because while there is a lot of information to learn, it also builds on previous concepts from general chemistry, a course most students want to forget!

But don’t worry!  StudyOrgo has you covered.  Our Editors have spent years tutoring and teaching Organic Chemistry to students and we have seen all of the pitfalls common to the first few weeks of the semester.  Our online platform allows members to learn organic chemistry concepts and mechanisms quickly and the material presented in an easy-to-follow format. Follow along with us and sign up with StudyOrgo today to help prepare you for all of your Organic Chemistry questions.

One of the concepts you will need to have mastered before you  begin the class is Intermolecular Forces.

Permanent covalent bonds hold atoms together by electrostatic interactions between atoms. But these bonds can be very different. As such, molecules are held together by electrostatic forces between the molecules built upon the type of covalent and ionic bonds in the molecule.  These interactions have been characterized on the electronegativity difference between the types of atoms in the molecule and are classified as three different types

  1. Dipole-Dipole Interactions

These intermolecular forces are the result of electronegativity differences between the atoms that result in the amount of net electron density around each atomic bond.  In order to talk about these forces, a few definitions are necessary.  Let’s take acetic acid as an example.  It has one C-O bond and one C=O bond.  The result of the electronegativity difference is that the amount of electron density on carbon is reduced significantly as a result of the C-O bonds.  This leads to an overall reduction in electron density on carbon, a delta positive charge (blue color of orbital), and a gain of electron density on the oxygens, a delta negative charge (red color of orbital).  There is no real “charge” but the probability of electron density is higher around the oxygens, making them appear to have extra electrons, like an anion would have.  The “flow” of this electron density results in the formation of a dipole, which makes up a polar covalent bond.

figure 1

Polar covalent bonds will interact with each other (red dipoles) in the “like-dissolves-like” concept you learned in organic chemistry.  The dipoles will interact with each other, the delta positive of one molecule will interact with the delta-negative of another molecule to create a dipole interation.

figure 2

  1. Hydrogen Bonds

When there is a hydrogen atom bonded to an element with lone pairs of electrons, it is possible for the delta positive hydrogen (the hydrogen bond donor) of one molecule to interact with the lone pair of electrons on another molecule (the hydrogen bond acceptor).

figure 2

This can happen for any molecules in solution, therefore protic solvents (such as ethanol) can form hydrogen bonds with itself while aprotic solvents (such as methylether) cannot. The result is easily seen in boiling point, which is 78C for ethanol but -23C for methylether.  One rule is that hydrogen bonds must be planar to the hydrogen donor an acceptor, so there are some constraints on structure.  This is what gives DNA its helical shape, which you will encounter in another course.

figure 5

  1. London-Dispersion Forces

These obscure forces are best described as very weak, very temporary dipole moments between non-polar covalent bonds.  Let’s look at butane, an alkane.  There is a temporary flow of electrons between each C-C bond and for an instant, a net dipole between each C-C bond.  This allows for temporary interaction with a neighbor molecule that has the opposite temporary dipole, and so on.  The effect is thousands of weak dipole interactions that add up to a large force, and the basis for what we refer to as hydrophobic interactions.

figure 4

Reviewing Acid Base Definitions

Posted on August 31st, 2016

Many students coming into organic chemistry have a difficult time with a concept that was covered extensively in general chemistry but often forgotten over the summer vacation.  This is the definitions of Acids and Bases.  It’s an important part of every mechanism in organic chemistry and your professor will likely assume you are an expert and jump right into the mechanisms whether you are ready or not!

We here at StudyOrgo have countless hours of combined experience tutoring students in just these situations to get you through the material and ready to ace the exam next month!  We have developed comprehensive explanations of the most common mechanisms, but have simplified their explanation in an easy to read format.  We also have developed a mobile app of our entire online content that members will be able to take advantage of while studying on the go!  Sign up with StudyOrgo today for help with Organic Chemistry this Fall Semester!

The classic definition of acids and bases are related to their ability to donate and accept protons into solution.  This is referred to as the Bronsted-Lowry Definition.  However, in organic chemistry, mechanisms are described by the flow of electrons.  Sometimes, an acids and bases can be thought of as their ability to donate and accept electrons.  Therefore, acids and bases were given definitions to reflect this feature.  This is referred to the Lewis Definition.

Type      Bronsted-Lowry Definition          Lewis Definition

Acid       Proton DONOR                                 Electron ACCEPTOR

Base      Proton ACCEPTOR                           Electron DONOR

 

Let’s look at two examples, first using the Bronsted-Lowry Definition.  Reaction of sulfuric acid (H2SO4, the acid) and acetate ion (the base) to produces hydrogen sulfate (HSO4-, conjugate base) and acetic acid (H3O+, conjugate acid).  In this case, sulfuric acid (the acid) donates the red proton to acetate, which can accept the proton with a lone pair of electrons.  Reaction of ammonia (NH3, base) with water (acid) produces hydroxide (OH-, conjugate base) and ammonium ion (NH4+, conjugate acid). In this example, water (the acid) donates the red proton to ammonia, which accepts the proton with one if its lone pare of electrons.

acid base 1

Now let’s look at the same examples, but using the Lewis Definition.  In the sulfuric acid and acetate example, acetate (the base) donates the red pair of ELECTRONS to the red proton on sulfuric acid, which gives the electrons from the green O-H bond back to oxygen to produce the conjugate base, hydrogen sulfate. In the ammonia and water reaction, ammonia (the base) donates the red pair of ELECTRONS to the red proton on water, which gives the electrons from the green O-H bond back to oxygen to produce hydroxide.

Both descriptions produce the same reaction, but are THOUGHT about differently.  In organic chemistry, you will mostly think about DONATING ELECTRONS, because this is what drives a reaction mechanism.

acid base 2

 

We hope you have found these explanations useful and encourage you to sign up today for more clear-cut definitions of many organic chemistry concepts this semester!  Good luck!

What to Expect for Organic Chem Fall Semester

Posted on August 4th, 2016

This semester you will start Organic Chemistry and you have likely heard a lot of rumors about the class; statements from upperclassmen like “it’s difficult”, “this class is impossible” or “the professor is horrible!” We here at StudyOrgo have helped countless students overcome the difficulties of this class and can help you before you even enter the class. We have over 20 years of collective experience tutoring and teaching Organic Chemistry and have developed a few helpful tips that have saved students from the seemingly crushing pressure of Orgo 1.

Hard Organic Chemistry Professor

StudyOrgo has over 180 reaction mechanisms typically covered in Organic chemistry and explained in an intuitive and clear manner available in an online format. We also offer the Quiz Mode to allow you to customize reactions and test your memory of important parts of all of our reactions. We offer simplified and illustrated descriptions of complex concept topics that you will encounter in your first few weeks in Orgo 1. We also have developed a mobile app for iOS and Android smartphones that allows you to study organic chemistry on the go! Sign up with StudyOrgo today to take full advantage of our system!

Here’s what you can expect in the first few weeks of Organic Chemistry 1.

  1. Most professors will spend the first class reintroducing general chemistry topics, but he or she will completely assume you received an A+ in general chemistry and have a full grasp of all these concepts! Refresh your memory of atomic structure, valence electrons, acids/bases and pH/pKa concepts. These will be used right away in Orgo 1. If you aren’t sure, ASK FOR HELP!!

Tip #1 – Look at a syllabus – Remember, your syllabus is an official contract between you and the professor. Professors are required to disclose what you are required to learn and what grading rubric will be used. Professors can usually remove requirements (to the delight of the students!) but cannot easily add them. Use this to your advantage! Highlight the contents or reactions of the book that will be required and use this to focus your attention when studying this semester.

  1. Professors will almost always begin quizzing the second week, the midterm is only 7 weeks away. Prepare for them early!!

Tip #2 – Schedule you’re studying! – Now that you know where the book is and a rough idea of what you are responsible for learning from the syllabus, take a calendar and divide the time you have to each test by the number of chapters. Schedule 2-3 hours a week to study and DON’T SKIP OR RESCHEDULE. Use your Smartphone calendar to send you alerts and reminders for your studying appointment.

  1. The class is about to go supersonic speed! Stay ahead of the pace of the class to avoid falling behind!!!

Tip #3 – Read ahead – The first week of Orgo2, read two chapters to get yourself ahead of the class. Don’t try to understand everything, just read the text and try to understand the big ideas. This will completely change the way you pay attention in class and allow you to spend more attention and ask questions about the details in class instead of scrambling to write down notes and drawings.

Tip #4 – Attempt ALL homework problems – When tutoring students, they are often intimidated when we ask them to try sample problems. But after a few examples, every student does them better and better with each new problem. Some students have even made comments such as ‘why didn’t I do this sooner?’ We were at StudyOrgo agree! It takes a lot of time, but practicing the problems will make it easier for the quizzes and tests.

Most importantly, RELAX!! With a little time management and help from StudyOrgo, you will have no trouble getting an “A” in Organic Chemistry this year!