Term3+IT+Home+Learning+-+Organic+Chemistry

Lesson 1 (for 4G2)

 * Learning Objectives**


 * You will learn the following by the end this lesson: **


 * (a) state that naphtha fraction from crude oil is the main source of hydrocarbons used as the feedstock for the production of a wide range of organic compounds. **
 * (b) describe the issues relating to the competing uses of oil as an energy source and as a chemical feedstock. **
 * (c) describe a homologous series as a group of compounds with a general formula, similar chemical properties and showing a gradation in physical properties as a result of increase in the size and mass of the molecules, e.g. melting and boiling points; viscosity; flammability **


 * Introduction to Organic Chemistry **

The classifications organic and inorganic were originally applied to a material on the basis of its source; the term organic was applied to products of living organisms and the term inorganic was applied if the material was characteristic of the non-living environment. In fact, until the German chemist Friedrich Wohler demonstrated in 1828 that an inorganic substance, ammonium cyanate could be converted in the laboratory to the organic substance urea, known to be produced by animals, it was believed that some special "vital force" found only in living organisms was needed to produce organic substances. (You can read more about Friedrich Wohler here: http://en.wikipedia.org/wiki/Friedrich_Wohler)

Today, organic chemistry is defined as the study of compounds containing carbon, whether or not they are formed by living organisms. Only carbonates and the oxides of carbon (CO2 and CO) are classified as inorganic even though they contain carbon.

Not only are all living things composed primarily of organic compounds, but there are also a host of man-made organic materials such as fabrics (nylon, polyester etc), cosmetics, plastics, paints, and medicines. Organic substances are virtually everywhere!



// **Check out this link to find out more about what Organic Chemistry is about and also its related job prospects:** //

http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=1188&content_id=CTP_003397&use_sec=true&sec_url_var=region1

There are at least //5 million// organic compounds up to date. There appears to be no limit to the number of compounds that are possible. Why is this so?

Cabon, being a group IV element, has four valence electrons; it therefore always forms 4 covalent bonds when it combines with other atoms.. Carbon can //join with other carbon atoms// to form

a. Long chain carbon atoms b. Branch chain carbon atoms c. Rings of carbon atoms d. Multiple bonds between carbon atoms and atoms of other elements


 * Bonding Possibilities in organic compounds**




 * Classification of Organic Compounds**

a. Hydrocarbons : Compounds containing carbon and hydrogen only b. Non-hydrocarbons : Compounds that may also contain other elements such as nitrogen, sulphur, halogen or oxygen atoms besides hydrogen and carbon.
 * 2 Groups**


 * Homologous Series**
 * 1) Organic compounds are further divided into sets or families with similar properties known as //homologous series//
 * 2) Compounds in each set have the same little group of atoms called the //functional group//
 * 3) Most //chemical properties// of organic compounds are due to the presence of the functional group




 * General characteristics****of each member in a homologous series:**


 * Can be represented by a //general molecular formula//
 * Each member has an Mr //14 units greater// than the preceding compounds (differ by a CH2 group)
 * // Physical // //property// //changes gradually// as the number of CH2 group increases
 * Have //similar chemical properties// (since they have the same functional groups)

//** Pls check out this cool song about homologous series: **//

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 * Sources of Hydrocarbons**

a. **Petroleum** (or __crude oil__) Complex //mixtures// of hydrocarbons. Formed from remains of small marine plants and animals under high pressure or temperature and bacterial action.

b. **Natural gas (mainly methane)** Formed from plankton and other sea creatures. Found //together// with petroleum.



Petroleum: A //miscible// complex mixtures of hydrocarbons with //close boiling points.// Method of //fractional distillation// is required to obtain the different fractions of petroleum.
 * Method to obtain Hydrocarbons**

Petroleum is heated in a furnace. Oil vaporizes and passes up the fractionating column. The different fractions come out of the column at different heights //depending on their boiling points//. Substances with //low boiling points// are collected near the //top// of the column




 * //Watch this video to learn more about fractional distillation of crude oil:// **

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 * Cracking**

To meet demand for fractions like petrol and kerosene, a process called //cracking// is carried out. This involves the use of //high temperature//, //pressure// and //catalyst// (aluminium oxide or silicon (IV) oxide) to split the larger molecules (of higher boiling points) into smaller ones (of lower boiling points). The mixture is then separated by fractional distillation.

Example:

C10H22 → C8H18 + C2H4

Cracking has three uses:

1. Big hydrocarbon molecules are broken up into small hydrocarbon molecules which can be used as fuel for motor vehicles. This is important as the amount of petrol fraction obtained from petroleum is insufficient to supply all the cars in the world. In fact, most of the fuel used in vehicles is produced by cracking.

2. Cracking is a way of making alkenes. Petroleum molecules are alkanes. When an alkane molecule is cracked, two or more smaller molecules are produced. At least one of these smaller molecules is an alkene. Usually a mixture of alkane and alkene molecules is produced. An example is the cracking of C18H38

**C18H38 → C8H18 (an alkane) + C10H20 (an alkene)**
Another possible reaction is: = C18H38 → C6H14 (an alkane) + 6C2H4 (6 ethene molecules) =

A lot of ethene is produced in cracking of alkanes. This is used to make chemicals such as ethanol and plastics such as poly(ethene).

3. Cracking is used to make hydrogen gas. An example is the cracking of C18H38

C18H38 → C18H36 (an alkene) + H2 (hydrogen)


 * Petroleum and Petrochemical Industry in Singapore**

** //Pls access this links to read more about the petroleum and petrochemical industry in Singapore:// **

Jurong Island: http://www.jtc.gov.sg/Portfolio/JurongIsland/Pages/index.aspx

Petrochemical Corporation of Singapore: http://www.pcs.com.sg/

**Competing uses for petroleum**

Most petroleum is used to provide fuels for burning. Only a small amount (naphtha) is used as a chemical feedstock to make useful materials such as plastics and chemicals. However, since there is only a limited amount of petroleum in the earth, many people believed it is wasteful to simply use it for fuels and believe that it should be reserved for making chemicals. If this is not done, a shortage of petroleum will result in a shortage of chemicals. If the petroleum runs out, it will not be possible to produce the plastics, drugs and other chemicals that we all take for granted today.

A possible solution is to find an alternative source for fuels. Examples of alternative fuels are ethanol and other types of biofuels, hydrogen and solar energy.

//**At the end of this lesson, test your knowledge in this simple quiz:**//

(Pls type in your name, class & index no. Pls click Full Screen before you start the quiz.)

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= **Lesson 2 (for 4G2)** =


 * Learning Objectives**


 * You will learn the following by the end this lesson: **

= Alkanes =
 * (a) describe the alkanes as an homologous series of saturated hydrocarbons with the general formula CnH2n+2 **
 * (b) draw the structures of branched and unbranched alkanes, C1 to C4 and name the unbranched alkanes, methane to butane **
 * (c) define isomerism and identify isomers **
 * (d) describe the properties of alkanes (exemplified by methane) as being generally unreactive except in terms of burning and **** substitution by chlorine **

Alkanes, as we have discussed earlier, are saturated hydrocarbons. The main source of alkanes is petroleum products and natural gas. Methane is one of the chief constituents of natural gas. Other alkanes are obtained from fractional distillation of crude petroleum.

Belongs to the homologous series of //saturated// hydrocarbons i. contains only //single covalent bonds// between atoms in molecules ii. contain only hydrogen and carbon atoms
 * Alkane Homologous Series**


 * Homologous series of alkanes**



**Physical Properties of Alkanes**


__**1.Physical state**__

Lower molecular weight alkanes are gases. Methane, ethane, propane and butane are gases at ordinary room temperature. Higher alkanes up to those having 17 carbon atoms are liquids; higher alkanes are solids at room temperature.

__**2.Melting and boiling points**__

Homologous alkanes show increase in melting and boiling points. Similar to the behavior of elements in the same group in a periodic table. There isn't much electronegativity difference between carbon and hydrogen, so there is hardly any bond polarity. The molecules themselves also have very little polarity. A totally symmetrical molecule like methane is completely non-polar. This means that the only attractions between one molecule and its neighbours will be Van der Waals dispersion forces. These will be very small for a molecule like methane, but will increase as the molecules get bigger. That's why the boiling points of the alkanes increase with molecular size.

__**3.Solubility**__

Alkanes, like all other organic chemicals are insoluble in water. They are however soluble in organic liquids. Alkanes are non-polar and are hence soluble in other non-polar liquids and not in water, as water is a polar molecule.

**Chemical Properties of Alkanes**
 * Similar for all alkanes
 * Not very reactive

// Reasons // :
 * Contains the same single C-H and C-C covalent bond
 * Strong C-C and C-H bonds require a lot of energy to break


 * Reactions of Alkanes**


 * 1. Combustion **

Alkanes are inflammable and are easy to catch fire. Complete combustion of an alkane leads to carbon dioxide and water. During combustion, the supply of oxygen has to be sufficient. Insufficient oxygen leads to the formation of carbon monoxide and the heat generated is less than when sufficient oxygen is available. The reactions are given below.



**2. Substitution Reaction with Chlorine** a. In the presence of //ultraviolet// light, methane can combine with chlorine to give a //mixture// of products (known as chloroalkanes) b. Light energy is used to start the reaction (by providing the energy to break the covalent bond between the chlorine atoms in Cl2) c. The chlorine atom (radical) produced then reacts with the alkane by substituting the hydrogen atom as shown



= **Methane** = Methane (CH4) occurs as a natural gas in the underground petroleum wells deep inside the earth. Methane gas is also known as marsh gas as it is emitted by bacterial decomposition of dead plants and animals. Methane is found in coal mine gases, gobar gas, sewage gas and bio-gas.


 * Uses of methane **
 * Because of its excellent burning, methane is used as a cooking gas.
 * Methane is used to produce carbon dioxide gas.
 * Methane is used to produce carbon black used in rubber industries.

Methane is used as a starting material for other organic compounds like methyl chloride, methylene dichloride, chloroform, etc

**Isomerism**

 * It is possible for alkanes with //more than 3 carbon atoms// to possess isomers.
 * Isomers are compounds with the //same molecular formula// but //different structural formula//


 * Example ** : Butane C4H10 has 2 isomers



**Alkyl Groups:**
The most common **alkyl groups** are discussed on this page. (They are also shown in example 11 in your workbook.) I would like to point out the similarities among these alkyl groups and the alkanes we discussed earlier.

Methyl Group
 Methane has one carbon and four hydrogens. The methyl group CH3 also has one carbon but only three hydrogens. In place of the fourth hydrogen, there is a bond to something else.



 Ethane has two carbons and six hydrogens. If any one of those hydrogens is removed and replaced with a bond to something else, you end up with an ethyl group, C2H5.


 * IUPAC Nomenclature: Rules for naming alkanes **
 * IUPAC Nomenclature: Rules for naming alkanes **

Nomenclature is the system of naming. With the existence of innumerable compounds of carbon, it has become necessary to follow a universal, rational system of naming. Such a system has been evolved by International union of pure and applied chemistry (IUPAC). By following this system, we can eliminate the confusion that arises due to usage of common names or trivial names.


 * 1) Find the //longest continuous chain// in the compound – basic name
 * 2) // Number each carbon atom // in the longest continuous chain starting from the end closest to the branch (which results in the use of smallest numbers)
 * 3) // Name the group // joined to the chain and state the no of the carbon atom to which the group is joined to
 * 4) If the chain has 2 or more __similar__ groups joined to it, prefixes like di-, tri-, tetra- is used to indicate the no of groups present
 * 5) If the chain has 2 or more __different__ groups joined to it, the groups are written in an alphabetical order/increasing size

 so its IUPAC name is butane. ||  || C - C - C - C
 * Let's go back to the two butane compounds. This compound has four carbon atoms lined up one after the other,

butane ||

C
 * The IUPAC name for the other structural formula is methylpropane (or 2-methylpropane). We come up with this name by looking at the fact that we have three carbon atoms in a row. That gives us **propane**. Then we have one carbon (with three hydrogens) attached to the side of propane. **Meth-** indicates that there is one carbon atom in the attached group. To show that it is a group of atoms attached to something else, we use a **-yl** ending. So this group of atoms is called a **methyl** group. The IUPAC name is **methylpropane**. The common name is isobutane. ||  || C - C - C

 methyl propane 2-methylpropane ||


 * As you will soon see, it can be necessary to indicate where a side group is attached to the main chain. This is done using a number that indicates to which carbon in the main chain a side group is attached. In this case, the methyl group is attached to the 2nd carbon of the propane, thus the full name is **2-methylpropane**. The **2-** is optional in this case because that is the only place the methyl group could be attached. ||


 * Isomers of pentane**

Pentane C5H12 has 3 isomers. They are shown below; the naming of the 2nd and 3rd isomers follow the rules above.







//** Watch the following video to help you understand isomerism better: **//

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**Short Quiz: Test Yourself!**
(Pls type in your name, class & index no. Pls click Full Screen before you start the quiz.)

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 * Assignment (Collaborative):**

This assignment is collaborative in nature. Pls work in teams of 3 or 4 from your class. Please use a platform like MSN or facebook to discuss with your team members about this assignment.

Your job is to

Choose a synthetic organic chemical which you think is the most important organic chemical in our lives.

Fulfil the following:

1. Name and chemical formula. 2. Share about its discovery. Who discovered it? 3. Why did you choose this chemical as the most important? 4. Identify at least one functional group

Example of important synthetic organic chemical:

Viagra



Then justify why you would have chosen this as the most important. Examples of fuctional groups are hydroxyl groups (OH) and C=C.