"Lesson 6 Basic Organic Chemistry, Part 2"
Lesson 6: Basic Organic Chemistry, Part 2 As we progress from hydrocarbons to more complex compounds, the nomenclature also becomes more advanced. Now you need to be familiar with Table 6.6 in your textbook. Once you are able to identify functional groups, we can begin to talk about reactivity. This requires you to have a firm grasp of the microscopic-to-symbolic link, as we will be using symbolic representations to illustrate the microscopic level. To help with this transition, you will use molecular model kits to help visualize molecules. Additionally, online tutorials and microscopic animations are available. Finally, online demonstrations of organic reactions will help with your macroscopic understanding. Ultimately, you will be able to predict products of organic reactions by understanding the chemical properties of the functional groups. Lesson 6 is about putting together all of the pieces. Up until now, you have had to take it on faith that all of these disjointed topics were somehow related. Here is where we begin to put it all together. In Lesson 5 you were taught all the basics you needed to begin to "talk shop" in organic chemistry. Now we are going to combine the ideas from Lessons 3, 4, and 5 to begin to explain how things work. We now have enough chemistry to explain what happens on a molecular level, which is a large part of what the last half of Chapter 6 is about. By the end of the chapter, you should be able to solve some simple organic problems and explain chemical phenomena yourself. We are going to break up the last half of Chapter 6 into two categories: interactions and reactions. Lesson Objectives When you have completed the material in this lesson, you will be able to: 1. Identify functional groups (circle and name). 2. Predict the effect of functional groups on physical and chemical properties. 3. Draw isomers. 4. Identify and define polymers. 5. Identify and draw stereoisomers. 6. Predict polymerization products. 7. Determine polymer monomer units. Key Concepts & Terms 1. Functional groups can be classified into various types (see Table 6.6 in your textbook). 2. Functional groups affect the chemical and physical properties of a molecule. 3. Functional groups affect the nomenclature of a molecule. 4. There are three types of isomers: structural, geometrical, and optical. 5. There are two types of polymers: addition and condensation. 6. Monomers are the building blocks of polymers. 7. Polymers are repeating chains of molecules. Reading Assignment: Chapter 6, Sections 3–6 Activities Lab 6, Three-Dimensional Geometry Online self-assessment quiz Quiz 6 Exam 2 What is the Difference Between an Interaction and a Reaction? An interaction is when two molecules that are close to each other have some sort of weak attraction or repulsion to each other–kind of like when you meet someone on the street and shake hands. These kinds of interactions usually take place in a collection of molecules, either a pure substance, or a mixture. For a quick review of mixtures, click here: http://brainpop.com/science/matter/compoundsmixtures/index.weml? &tried_cookie=true). A reaction is when two or more atoms or molecules bump into each other with enough force that they rearrange and form new molecules. This is a strong force! To continue our analogy, this would be when two people meet and get married. Another name for an interaction is Intermolecular Forces (IMFs). For a quick overview of intermolecular forces, see http://chemed.chem.purdue.edu/genchem/topicreview/bp/intermol/in termol.html. To view the intermolecular forces in water on a microscopic level, click http://programs.northlandcollege.edu/biology/Biology1111/animations /hydrogenbonds.html. To compare the intermolecular forces in non-polar compounds, see http://www.chemguide.co.uk/atoms/bonding/vdw.html#top and http://www.chemguide.co.uk/atoms/bonding/hbond.html#top. Here are microscopic representations of salt dissolving in water: http://programs.northlandcollege.edu/biology/Biology1111/animations /dissolve.html and http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/mo lvie1.swf. Intermolecular forces explain why some things dissolve in water (like salt or sugar), but some do not (like oil). If the IMFs of two compounds are similar, they dissolve. If not, they form two different layers, and we say they are immiscible. For an explanation of solubility, see http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch18/solubl eframe.html. This is the very concept that is exploited in soap! <<Insert picture of soap molecule: see below>> Soap is made up of a long tail, which is made of carbons and hydrogens. It is very non-polar, so it dissolves oil and dirt from your hands. The "head" of the soap is a carboxylic acid group, which is very polar. It likes to interact with water, because they have similar IMFs. Thus, the soap molecule acts as a link to lift the oil off your hands and wash it down the drain! Check out his site for a more detailed model of soap. http://antoine.frostburg.edu/chem/senese/101/consumer/faq/making- soap.shtml Now use chemistry to explain what is wrong with this website: http://www.suncitysoap.com/chemistry.html ? <<Insert answer here: everything is a chemical, so Suncity Soap contains chemicals, too. The milk, water, and oils that they use to make their soaps are all chemicals.>> Another practical application of IMFs is dyeing. Below is the structure of a segment of cotton (the material jeans are made of) and indigo fabric dye (used to color jeans). Can you explain why indigo sticks to cotton? What IMF is involved? Can you explain chemically why blue jeans fade after many washings? <<Insert answers here: Indigo is a polar molecule and so is cotton, so they stick to each other through IMF's. In fact, because Indigo has N--H bonds and cotton has O--H bonds, they both undergo Hydrogen bonding, the strongest type of IMF. Because it is an IMF and not a true bond, over time, your jeans will fade. Each time you launder them, the water molecules can form Hydrogen bonds with Indigo and with the cotton. Thus, water molecules come in and disrupt the H-bonds between Indigo and cotton, forming new H-bonds between water and cotton, and between water and Indigo. This makes the Indigo soluble in water, so it is washed away with the laundry water. >> Indigo Starch Here is the structure of wool. Would you expect indigo to be a good dye for wool? Why or why not? <<Insert answers here: Yes, Indigo would be a good dye for wool. Wool is a protein structure, made up of lots of polar groups that can hydrogen bond (notice the --OH and --NH2 groups). Because it has lots of H-bonding sites, it can accept the Indigo dye. >> Actually, hair dye works in a similar way. Your hair is made up of proteins, which look surprisingly similar to the structure of wool, which is also made of protein. You know that there are two types of hair dyes on the market: permanent, which lasts for many months, and temporary, which fades away after several washings. Can you predict what kind of interaction or reaction is going on in each case? Why does the temporary dye fade away after several washings? <<Insert answers here: Permanent hair coloring uses a chemical reaction to modify the structure of your hair. Temporary hair coloring simply adheres to your hair through Hydrogen bonding, so it will wash out after several showers.>> How about applications to pharmaceuticals? Consider the popular antibiotic amoxacillin, which is used to treat any number of sinus, nasal, and ear infections, shown here. When making a drug, manufacturers have to decide how to offer it: as a water-based solution (for things that are soluble in water), in pill form, or as a suspension (for things that are not water-soluble). How do you expect the pharmacy to offer this drug? Why? <<Insert answers here: While most anything can be offered in pill form, including amoxacillin, this drug is water soluble because of all the polar groups around the molecule. Notice the --NH2 groups, --OH groups, and C=O groups, all of which are polar. >> Here are some practical applications of IMFs: http://antoine.frostburg.edu/chem/senese/101/consumer/faq/starch- thicken.shtml http://chemed.chem.purdue.edu/demos/main_pages/24.16.html http://chemed.chem.purdue.edu/demos/main_pages/24.14.html http://chemed.chem.purdue.edu/demos/main_pages/24.15.html http://chemed.chem.purdue.edu/demos/main_pages/24.17.html What about Reactions? So far, we have been looking at chemical interactions. Now let's shift our focus to chemical reactions--specifically, organic polymer chemical reactions. Your book focuses only on polymers in this chapter, although we will expand this discussion to other types of organic reactions later in the course. There are two types of polymerization reactions: addition and condensation. We will go into these in detail, and you will be expected to be able to classify the types and predict the products of the reactions. For a brief overview of the process of polymerization, view http://www.chem.rochester.edu/~chem421/stepchn.htm. What are Polymers? <<Insert picture of plastics here: See below, from website http://images.google.com/imgres?imgurl=http://www.uoregon.edu/~recy cle/Website%2520Photos/recy_items/plastic.jpg&imgrefurl=http://www. uoregon.edu/~recycle/Material_photo_signs_text.htm&h=288&w=432&s z=32&tbnid=LFs5AXDCiwAJ:&tbnh=82&tbnw=123&start=6&prev=/ima ges%3Fq%3Dplastic%2Brecycle%26hl%3Den%26lr%3D%26ie%3DUTF- 8>> First, you need to understand what a polymer is. Loosely speaking, a polymer is a repeating chain of one or more simple chemical units. You are probably familiar with synthetic polymers, such as nylon, plastics, and Styrofoam. These are made up of repeating chains of monomers, such as those shown in Table 6.9 in your textbook. But did you know that wood and hair are also polymers? These are natural polymers. <<Insert pictures of wood, hair here: See below, from http://neon.roons.dyndns.org/hair- pfx.jpg and http://www.rti.org/page.cfm?objectid=5EC62FBF-8F62-4B55- A090DDF678063DB6 >> Nature knows how to make polymers, too! The method is relatively simple. So, now that you know what polymers are, let's look at their reactions: Addition. An addition polymer has just one type of monomer, repeated over and over again. If A is the monomer, the polymer looks like this: -A- A-A-A-A-A-A-A-" This is how things like PVC and Styrofoam are made. To understand the mechanism, look at Figure 6.26 in your textbook. For further explanation, visit. http://mrcemis.ms.nwu.edu/polymer/3-addition.html, http://www.chemguide.co.uk/mechanisms/freerad/polym.html#top and http://www.chem.rochester.edu/~chem424/ppo2.gif . Condensation. In a condensation reaction, two different monomer units are used. If the two different monomers are A and B, then the polymer looks like this: -A-B-A-B-A-B-A-B-A-B-. The reason it is called a condensation reaction is that when A and B react together, they give off water! This is how nylon and polyester fabrics are made. For a macroscopic demonstration of how nylon is made, click here: http://chemed.chem.purdue.edu/demos/main_pages/25.1.htm. To see how condensation reactions work microscopically, view these sites: http://www.tvdsb.on.ca/westmin/science/sbioac/biochem/condense.ht m and http://mrcemis.ms.nwu.edu/polymer/4-condensation.html#Part6. Polymers have amazing properties on the macroscopic level. To view some of the various properties of polymers, click on the demonstrations below. http://www.psrc.usm.edu/macrog/index.htm http://www.lbl.gov/MicroWorlds/Kevlar/ http://chemed.chem.purdue.edu/demos/main_pages/25.2.htm http://chemed.chem.purdue.edu/demos/main_pages/25.3.htm http://chemed.chem.purdue.edu/demos/main_pages/25.4.html http://chemed.chem.purdue.edu/demos/main_pages/25.5.html http://chemed.chem.purdue.edu/demos/main_pages/25.6.html http://www.chem.leeds.ac.uk/boronweb/ormsby/lect_demos/animatio ns/foam.html What do Isomers Have to do with Reactions? We began talking about isomers in Lesson 5, but you will notice that isomers are brought up again at the end of Chapter 6. The reason that we bring them up again is because reactions can make different kinds of isomers. There are actually three kinds of isomers: 1. Constitutional Isomers. We talked about the isomers in Lesson 5. They have the same chemical formula, but different connections between atoms in the molecule. 2. Geometric Isomers. Sometimes these are called cis/trans isomers. These molecules have either a double bond or a ring in them. When a chemical reaction forms a double bond (or a ring), the two other groups attached to the carbons on each side of the bond can be in different places. After the double bond (or ring) is formed, the molecule cannot twist and rotate anymore, so the geometry is fixed. For a detailed explanation, see http://www.chemguide.co.uk/basicorg/isomerism/geometric.htm l#top. Check out http://scholar.hw.ac.uk/site/chemistry/topic4.asp?outline for more information and simulations. 3. Optical Isomers. These are the trickiest isomers to identify; yet they are the most important for life! Optical isomers are nonsuperimposable mirror images. Your hands are optical isomers: you cannot lay them one on top of the other exactly. Likewise, a carbon with four unique groups attached to it can have a nonsuperimosable mirror image. These molecules are called chiral compounds. The best explanation and practice is at http://www.nobel.se/chemistry/educational/poster/2001/game.h tml. You can also check out http://www.chemguide.co.uk/basicorg/isomerism/optical.html#t op and http://www.elmhurst.edu/~chm/vchembook/209optical.html. Optical isomers are so important because our bodies are pre- programmed to only accept one isomer of various organic compounds, including vitamins and drugs. Have you ever gone to the drug store and looked at the vitamin isle? You will see things like l-Lysine–now you will understand what you are seeing! To see an ever-greater practical application of optical isomers, see http://www.chm.bris.ac.uk/motm/thalidomide/start.html, including the sub-links. (Be sure to see http://www.chm.bris.ac.uk/motm/thalidomide/optical2iso.html!) Now, you have enough organic chemistry to understand and appreciate these websites: http://www.nearingzero.net/screen_res/nz079.jpg http://www.nearingzero.net/screen_res/nz081.jpg