Simple Functional Groups

Help me with Organic Chemistry

Simple Functional Groups
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"Help me with Organic Chemistry"
Caption: Simple Functional Groups
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Understanding Organic Chemistry

Table of Contents:
1. Introduction – the Importance of Carbon
2. Hydrocarbons
3. Commonly Seen elements
4. Organic Functional Groups
5. Naming of Carbon Containing Compounds
6. Conquering Organic Chemistry

1. Introduction - the Importance of Carbon

On the first day of any class of Organic Chemistry, the instructor will invariably talk about one element more than any other – Carbon, or the 6th element found on the Periodic Table of the Elements. Organic Chemistry originated with the study of living things, and the patterns of behavior of the molecules which contain carbon were identified. The belief was formed that all organic molecules (which at the time, simply meant “things which live”) must have carbon. According to research which has occurred since then, it has become apparent that the same rules which govern carbon containing compounds may be found in a select few molecules which don’t contain carbon, but in general, the study of Organic Chemistry will be defined by molecules containing carbon. One of the first characteristics which should be understood about carbon is that in the vast majority of situations, it will form four bonds. This can consist of four single bonds, two single bonds and one double bond, two double bonds, or one triple bond and one single bond. This will become more apparent below.

2. Hydrocarbons

Carbon, however, as important as it is, is not the only element which must be understood for Organic Chemistry. Hydrogen, the 1st element, is the next most used element, as a healthy majority of the molecules studied will contain it. The most simple type of organic molecule is the Hydrocarbon. A hydrocarbon is formed of exactly what its name implies – only hydrogen and carbon atoms are found in the molecule. These are often referred to as “fatty”, or “greasy”, because the longer the carbon chain, the more “oily” it becomes.

To illustrate this, gasoline is a hydrocarbon which is made up of a mixture of hydrocarbons which consist of carbons linked together in a straight chain. This mixture is composed of different hydrocarbons with 6-8 carbons in a row, and hydrogen atoms are bonded to each carbon. Because the chain is relatively short in length, gasoline doesn’t have a very oily feel to it. However, motor oil consists of chains containing 18-34 carbons linked together. This is because of the non-polar nature of carbon-carbon bonds and carbon-hydrogen bonds. Organic Chemists who choose to study hydrocarbons will verify that the topic can become very complex, but the typical Organic Chemistry class will only focus on some simple behaviors of hydrocarbons as well as the naming of them. As explained in Part 5, hydrocarbons are by far the easiest molecules to name.

3. Commonly Seen Elements

Carbon and Hydrogen are joined by a plethora of other elements seen in organic molecules, but there are several specific contributors which are vitally important to all manner of living things. Elements near the top of the Nitrogen group, the Chalcogen group, and the many of the Halogen group are present in many molecules. In general, the most important element out of these groups is Oxygen. Oxygen plays an important role in the majority of reactions which are commonly studied in Organic Chemistry, because it is found in many functional groups. Following this, Nitrogen, Bromine, Chlorine, Iodine, Fluorine, Sulfur, and Phosphorous are all very important. Classes which are focused on the Biology aspects of Organic Chemistry (especially Biochem) are more likely to see sulfur and phosphorous containing molecules, but even a class which is designed purely to advance the student in the study of Organic Chemistry in general will touch on these elements.

Understanding the importance of the roles which each of these elements play in reactions between molecules will greatly accelerate the learning process of the student. For instance, oxygen is a very polar molecule, due to the two pairs of lone electrons which it retains after forming two bonds and satisfying its formal charge. Through this polarity, due to the lone electron pairs, oxygen facilities the breaking of and formation of many types of bonds, which can result in synthesis (two molecules joining together), single displacement (when one element is traded for another), and other types of chemical reactions. As important as these reactions are, it is evident that these additional elements do play a vital role in understanding Organic Chemistry.

4. Organic Functional Groups

Functional Groups range from incredibly simple to rather complicated, but it is important to understand how simple the definition is: a functional group is a recognizable portion of an organic molecule which behaves in a predictable, distinct way. (Note: it is strongly advised to look up a chart showing various functional groups to visualize the descriptions below, as they will make much more sense with a visual reference.) Very simple functional groups include single, double, and triple bonds between carbons atoms (known as alkanes, alkenes, and alkynes) and alcohols (a carbon that is bonded oxygen bonded to hydrogen, as in C-O-H). These may seem complicated at first, but they must simply be memorized. Different people use different techniques, but it is very important to find a method to make as many concepts as simple as possible. For instance, the names of these bonds differ by only one letter. A method which is used often to remember that single, double, and triple bonds are named as they are is to remember the order which the letters come in the alphabet. Since these letters can be imagined in alphabetical order, or “a” before “e” before “y”, they can be matched in sequence to the naming of the types of bonds. Single bond = “a” or alkane, double bond = “e” or alkene, and triple bond = “y” or alkyne. Such tricks may seem simple or tacky, but as difficult a topic as Organic Chemistry is, the more tricks such as this one which may be devised and remembered, the better.

Of course, there are more complicated functional groups as well. These are easier to remember if one builds off of the memorization of simpler groups, but they all must eventually be memorized. For instance, a carbonyl carbon is described as a carbon in some type of chain which has a double bond to an oxygen atom (C=O). This group is important, because it is present in many functional groups. A ketone is a single carbon in a carbon chain which also has a double bond to a single oxygen atom. Two other groups may be memorized based off of this format. An aldehyde replaces one of the carbons in the chain with a hydrogen atom. This means that instead of the main carbon which has the double bond to the oxygen being bonded to two other carbons, one of the carbons is instead hydrogen. If a carbon atom is instead replaced by a halogen, it is instead named an acyl halide. Understanding functional groups is vital for the next step, which is the naming process for organic molecules.

5. Naming of Carbon Containing Compounds

It is impossible to explain naming in its entirety in a single page, or even a full chapter of a textbook. This is because the enormous variety of functional groups, as well as the almost limitless number of potential combinations of these groups. Even the specific position in the molecule of each of these groups is required to form a proper name. Because of this, an organization known as IUPAC (the International Union of Pure and Applied Chemistry) has created and updates yearly a book of naming principles which is larger than two or three of the average Organic Chemistry textbooks stacked on top of each other.

Even more frustrating is the fact that a large number of the more commonly seen molecules were used so often prior to the formation of these rules that they have what are known as common names. Common names are often heard in the laboratory, or in papers written on topics in Chemistry, but a student must learn all of the proper naming conventions which can be dramatically different from the common names. Examples include acetone, the simplest ketone in existence. Acetone is the common name, but according to the naming rules, it should instead be called propanone. This is especially frustrating when performing experiments in the lab, because often the book will refer to a molecule by its common name, when you must find it based on its IUPAC name, and vice versa.

However, there are conventions which must be memorized by every Organic Chemistry student in order to get anywhere in the study of the discipline. Names for carbon chains are a great example. The first 10 names applied based on the number of carbons in the main or parent chain should be memorized, although it is possible that a professor may require more. These prefixes (which will be combined with various suffixes to describe different functional groups) in order are meth- for 1 carbon, eth- for 2 carbons, prop- for 3 carbons, and continuing in order: but-, pent-, hex-, hept-, oct-, non-, and dec-. Some of these may be memorized using simple acrostics, such as “Monkeys eat peeled bananas” to remember the first 4 in correct order. Other methods include comparing to commonly known names, such as the octopus which has 8 arms, or a hexagon which has 6 sides.

This is only the very tip of the iceberg as far as naming rules go. The suffixes which are combined based on functional groups are also very important. For instance, the primary alcohol which humans drink is known as “ethanol”. According to the naming rules, “eth-“ in ethanol stands for a molecule which contains 2 carbons. As was learned in Part 4, an alkane has a single bond between carbons, so the “-an-“ in ethanol shows that there is a single bond between the 2 carbons. And the proper suffix for naming an alcohol, or a molecule containing a combination of (-O-H) connected to a carbon is “-ol”. Put these all together, and the name also comes together – ethanol. This is a very simple molecule, however, and the naming rules become exponentially more complicated as the number of functional groups in a single molecule as well as the way in which those functional groups are arranged increases. This helps to demonstrate the importance of memorizing the names of functional groups, followed by the suffixes which go along with them.

6. Conquering Organic Chemistry

All of the above just scratches the surface of Organic Chemistry. On community college campuses, it is often recognized as the hardest class one may take. At 4 year universities, it is the single class which weeds out the highest number of students who plan to go on into scientific fields which include it as a prerequisite. Because of this, intense study is required to conquer it. If possible, arrange to take an easy class load in combination with this class. Also, it is important to plan on devoting more time outside of class than the vast majority of other classes which were preparation for this course. Read the textbook. Any possible method of memorization is a valid and valuable resource. The use of notecards is possibly the biggest distinction between those who pass and those who fail out of Organic Chemistry. Make many of them, and post them everywhere in the home. Use them during lulls between classes, or on public transportation. Learn the acrostics, the rhymes, and as many other tricks which have been used by past Organic Chemistry students. Take extensive notes, and record lectures if possible. This is one course which cannot be taken lightly.

However, do not panic as a result of reading the above. As difficult a subject as it is, it is completely conquerable. Taking it seriously and studying everything as it is learned is a sure pathway to success. Never get behind, ever. Consult with previous students regarding preferred professors, and attempt to establish an understanding of the priorities of the professor as soon as possible to learn the most important topics to study in preparation for tests. If necessary, and funds are available, hire a tutor. Go online, research outside of class and even outside of the textbook. Many sites offer free tests to establish what topics are the strongest and which need to be studied more.

Most importantly, realize that tens of thousands of students have taken this course and succeeded. Work put in will equal results put out. This is a class which it is possible to master, and it will help to determine the direction of study to take after this class is over. Realize that it is required for many fields of study because it is very helpful to know. Finally, do all you can to have fun! Find fellow students who are taking it, and like it, or want to study it more. They will help provide motivation and may provide a network of assistance due to various levels of understanding of different topics of study.

Go forth and conquer!

More about this author: Paul Stanphill

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