Unit 3  Organic Chemistry
Are You Ready?   Page 176  Answers  
 
So far we have dealt with the metals and non-metals and the compounds made up from them. Group 14 on the periodic table. The Carbon group, was deliberately avoided because of the material involved in ORGANIC chemistry. All of the inorganic chemicals known worldwide number approximately 50,000 but the number of organic compounds number 500,000 and about 2,000 more are added each year.
 
Organic chemistry is the study of compounds made primarily from carbon. These compounds have unique properties based mainly on the fact that carbon can bond to itself covalently almost indefinitely. The most important aspect of the atoms involved in organic chemicals are their valence bond electrons.
 
A quick review is needed. Carbon has four valence electrons which results in 4 covalent bonds. Hydrogen has only one electron and has only one covalent bond. Oxygen has 6 valence electrons but 4 are bound up in two lone pairs leaving only 2 single bonding electrons. Nitrogen has 5 valence electrons but 2 are bound in a lone pair leaving 3 covalent bond electrons. Most of the other elements follow this same general rule.
 
       |                   /
   - C -    H-   -N      -O-    -S-     Cl-   Br-
       |                   \
 

Activity 3.1 Testing Fats and Oils

Hydrocarbons
Hydrocarbons are the simplest of all the organic molcules.  They consist of only carbon and hydrogen, hence the term hydrocarbon.   The very simplest of all the hydrocarbons is methane.

 
It can be shown in one of three ways.

Molecular                       Structural                            Skeletal
Formula                          Formula                              Formula
                                            H
                                             |                                              |
   CH4                             H - C - H                                   - C -
                                             |                                              |
                                            H
 

Each type of formula has its own benefits. Molecular formulas show what is in a compound but very little about how the atoms are put together. The structural formula shows the position of each atom and its relationship to every other atom, but it is time consuming to write out. The skeletal equation shows all covalent bonds, and all atoms except hydrogen.
 
Organic chemistry uses certain prefixes that indicate the number of carbon atoms in a particular molecule. You should memorize these if you have not already done so.
 
Number Prefix
1     meth
2     eth
3     prop
4     but
5     pent
6     hex
7     hept
8     oct
9     non
10   dec
11   undec
12   dodec
 
There are of course more but these will be sufficient for this course.
   
The Alkanes
Using methane, CH4, as a starting point we can add more carbons, one at a time, and more hydrogens to fill out the bonds on the carbons. This first group is called the alkane series and it has the general formula:  
CnH2n+2
Alkane series
Name Formula mol. wt. m.p. b.p.
methane CH4 16.04 -182.48o -164oC
ethane C2H6 30.07 -183.3  -88.63
propane C3H8  44.11  -189.69  -42.69
butane C4H10 58.13 -138.35 -0.5
pentane C5H12 72.15 -129.72 36.07
hexane C6H14 86.18 -95 68.95
heptane C7H16 100.21 -90.61 98.42
octane C8H18 114.23 -56.79 125.66
nonane C9H20 128.66 -51 150.80
decane C10H22 142.99 -29.7 174.1
undecane C11H24 156.32 -25.59 195.90
Look at the list very carefully.  Each successive compound increases by only CH2. Also the molecular weight increases by only 14.03, that is CH2.   It also seems that as the length of the carbon chain increases from 1 to 11 the melting point increases as well as the boiling point.
 
All of the above are straight-chain alkanes. That is, each additional carbon is added to the end to form one long continuous chain and there are only single bonds in the main chain of the molecule.

For example:


              propane                                                                    octane
 
Propane has three carbons in a main chain, hence, prop, and there are only single bonds in this main chain therefore (ane). Octane has eight C's in a main chain hence, oct, and again the main chain has only single bonds between beach carbon therefore it is an "ane". Both of the above are members of the alkane series. Draw several more to verify for yourself how these compounds are put together.
 
IUPAC Rules For Naming Organic Compounds.
(International Union of Pure and Applied Chemists)
1. Find the longest continuous carbon chain. Count the number of carbons in it and determine the prefix.
 
2. Check to make sure that all the bonds in this long chain are single. The ending will be "ane"
 
3. Put the prefix and ending together.
 
Naming compounds with side chains
How do we name something like this? 
 
First find the longest carbon chain. It has 11 carbons in it therefore this compound is a "undec" something. Check to see if it contains only single bonds. It does, therefore it is an "ane" as well. The compound is a "undecane". What about the C-C group?
 
Two carbons is "eth" and it has single bonds therefore it is ethane but it is attached to the longer chain. Take the "ane" off and add "yl". This is an ethyl group. If you count bonds it is not C2H6 but it is in fact C2H5-. The "-" indicates the point of attachment to the long undecane chain. So this compound is ethylundecane. But where is the "ethyl" group attached. Start counting from the end of the undecane. The ethyl group is either 5 from one end or 6 from the other end. When this happens always choose the lowest number. So we can name this as  5-ethylundecane. That is, an 11 carbon alkane called undecane with an ethyl group stuck on it at the 5th carbon from the end.
 
IUPAC Rules For Naming Branched Compounds
1. Determine the longest continuous chain, this will be the parent chain. Give the parent chain a prefix matching the number of carbon's in it.
 
2. Assign #'s to each C of the parent chain so that the numbers of all attached side pieces add up to the smallest sum.
 
3. Determine the correct name for each branch or other atom or group.
 
4. Attach the name of the alkyl group or other substituent to the name of the parent as a prefix. Place the location # in front and separate from the name by a hyphen.
 
eg.     3-methyl-heptane
 
Parent chain is 7 carbons long with all single bonds, therefore heptane. Side group is one carbon, therefore "meth" and because it is attached to the parent we add "yl" so we get methyl. The methyl group is attached to the parent chain at carbon number 3 not carbon number 5. Count for yourself. Put it all together 3-methylheptane.
 
5. When 2 or more groups are attached, name each, and locate them by number. Always use hyphens to separate the #'s from each other.
 
eg.  3-ethyl-5-methyl-octane
 
Ethyl comes before methyl alphabetically, it just happens to come that way numerically in this example as well.
 
eg.  4-ethyl-3-methyl-octane
 
In this example ethyl still comes first alphabetically before methyl. The numbers that locate their point of attachment go with them.
 
6. When 2 or more of the substituents are identical, use special prefixes such as "di" for 2, "tri" for three and "tetra" for 4 and specify the location #'s of every group.   eg. 
2,4-dimethyl-hexane (OK)    2-methyl-4-methyl-hexane (NO)     3,5-dimethyl-hexane(NO)
 
7. When identical groups are on the same carbon in the parent chain, repeat the number on the parent 
carbon.    eg. 
 3,3-dimethyl-pentane (OK)    3-dimethyl-pentane (NO)     3,3-methyl-pentane (NO)
 
Add-on Substitution Groups
The following are substitution groups that can be added on to a main parent chain.

methyl

ethyl

n-propyl


iso-propyl


n-butyl


sec-butyl


tert-butyl


In addition to the above there are the halogen substitution groups:
F is fluoro
Cl is chloro
Br is bromo
and I is iodo

Go to Organic Worksheet #1 - Simple Chain Nomenclature

 
The Alkenes  
An alkene is simply a C=C, that is a double bond between two carbon atoms. The position of the double bond will often determine what is the parent chain. If a double bond exists then the parent chain must include it. The double bond also uses up 2 bonds that normally hold hydrogen so the general formula for alkenes is CnH2n. The double bond also locks the molecule in a certain position so that attached groups can't rotate around the double bond. This means some special naming conventions.   Easy stuff first:
 
 Name            Formula
Ethene          CH2=CH2
Propene        CH2=CH-CH3
Butene          CH2=CH-CH2-CH3     or      CH3-CH=CH-CH3
 
There are two structural formulas for butene. This is because the double bond can come between the 1st and 2nd C or between the 2nd and 3rd carbon. We get around this by naming the position of the "ene". You'll also have noticed that the names have changed from "ane" to "ene" indicating the presence of a double bond.
 
CH2=CH-CH2-CH3     but-1-ene                    CH3-CH=CH-CH3      but-2-ene
 
These two are isomers. They have the same molecular formula, C4H8, but different structural formulas. We also have a new problem.

              cis-but-2-ene                                            trans-but-2-ene
 
The cis means (same side) and the CH3- methyl groups are both above the C=C bond and on the same side (top). Trans means transverse and the CH3- methyl groups are in a trans position to each other across the C=C bond.
 
Some more examples:
The longest chain of carbons is 7. Therefore this is a "hept" molecule. There is also a C=C double bond therefore it is a heptene. Counting from both ends the double bond starts at either 3 or 4. Choose the lowest number. The molecule is now hept-3-ene. The longest chain is also split around the C=C bond in a transverse fashion therefore it is also trans-hept-3-ene.
 
This accounts for everything about the parent chain. Since we choose the C=C number to be 3 we have now locked in place a numbering system for this molecule. That means there is a methyl group at carbon 4. The name of the molecule is therefore:   4-methyl-trans-hept-3-ene.
 
example 2:
Look for the longest continuous carbon chain. There are 9 carbons therefore it is a "nona" and there is a C=C at carbon 4 therefore it is non-4-ene. The sides of the chain of the parent are both on the same side. In this case, on top of the double bond therefore it is cis-non-4-ene. There is a methyl group at carbon 4 and an ethyl group at carbon 5. Therefore the full name is 5-ethyl-4-methyl-cis-non-4-ene.

Go to Organic Alkene Series Worksheet
           
The Cyclic Alkanes   (Cycloalkanes)  
When does an alkane act like an alkene?
When its cyclic! Some alkanes circle around and join up with themselves. They lose two hydrogens when they join up and so cyclic alkanes have the same general formula as alkenes (CnH2n).

cyclobutane (C4H8

  cyclopropane (C3H6

cyclohexane (C6H12
What would iso-propyl-cyclopentane look like?
The parent ring will be 5 C's and 10 H's. Then pick any of the C's and remove a hydrogen and replace it with an isopropyl group.
       iso-propyl-cyclopentane
 
Cyclic compounds can also have cis and trans configurations because things can stick up or down below the equator of the molecule.

Go to Organic Cycloalkanes Worksheet
    
The Alkynes 
The alkyne series is very similar to the alkane and alkene series. They all have at least one triple bond. Please note the fact that a single letter change results in a dramatic change in the structure of a compound.
 
Alkyne Formula
Ethyne  C2H2                                                                         Propyne C3H4

Butyne C4H6
                                   but-1-yne                                                                     but-2-yne
 
And the pattern continues just as it did for the alkanes and alkenes. The general formula of an alkyne is CnH2n-2. The triple bond prevents rotation but it also prevents the formation if cis and trans structures in the parent chain.
 
In the event a parent chain has both an alkyne and an alkene the alkyne is more important.
 
example 
 
8 carbons long therefore an "oct". Has both alkene and an alkyne bonds. The alkyne is the most important therefore number so that it has the lowest possible number. Therefore we now have "3-yne" and an alkene at 5 and at 7. Therefore the full name would be oct-5,7-diene-3-yne.
 
All the other rules previously learned still apply.

  Go to Organic Alkenes and Akynes Nomenclature Worksheet

Extension Exercise 3.1  Naming and Drawing Hydrocarbons
Extension Exercise 3.1  Condensed Structural Fotmulas


Isomers
Isomers have the same chemical formula but different structure.  The more carbon atoms in a formula the more isomeric structures that are possible.
Activity 3.3 Building Molecular Models

Extension Exercise 3.2  Identifying Isomers
Combustion of Hydrocarbons
Combustion is a reaction with oxygen which produces heat as a result.  Hydrocarbons react with oxygen to produce carbon dioxide and water as products as well as heat.  The hydrocarbon that burns is referred to as a fuel.  

 fuel    +   oxygen ----->   water vapor   +   carbon dioxide

When there is not enough oxygen present, water still gets created but carbon canonly grab one oxygen aton resulting in carbon monoxide.    Carbon monoxide is a clear, colorless, odourless gas which is a toxic poison.

fuel   +   inadequate oxygen  ----->  water vapor   +   carbon monoxide  


Addition Reactions
1.  Halogenation with light:
       This is a substitution reaction:

       R-H + halogen  -----------> R-F, R-Cl or R-Br        +      HF, HCl or HBr     (R can be any alkane)
                                    light
                    butane                                                                 chlorobutane



2.  Dehydration
      This reaction removes water from a molecule. It works great on alcohols.

Works best for 3o alcohols > 2o alcohols > 1o alcohols

eg.   iso-propyl alcohol being dehydrated into propene and water

.
The acid works by pulling off a H2O molecule from the organic molecule. Once formed the H2O stays in the acid because the acid is very hydrophilic (water loving). During dehydration and the formation of an alkene 2 products always form depending on the rotation around the original single bond.  When the hydroxyl group is in the middle of a odd numbered molecule the should be only one product.  Because of the double bond there is the possibility of getting cis, trans isomers forming.  If a diol is present both alcohols will be removed and an alkene bond will form.

        pentan-3-ol                                          cis-pent-2-ene          trans-pent-2-ene

Reactions of the Alkenes and Alkynes
                                     Markinikov's Rule:
When a substitution is made across a C=C or triple bond the H will be added to the carbon that already has the most H's on it.  When a dehydration occurs across a C=C or triple bond then the H removed will be from the C that has the most H's on it.

3. Addition of Hydrogen
    This is an addition or saturation reaction.

         unsaturated                                    saturated
        hydrocarbon                                  hydrocarbon

eg.  pent-2-ene being changed into pentane


eg, 2 ethyne (acetylene) being converted into ethane


4.   Halogenation
        The addition of a halogen also called chlorination, bromination or iodination, etc). Trans addition is preferred over cis addition.

eg.  2-methyl-propene is halogenated with bromine to 1,2-dibromo-2-methyl-propane

As the halogen adds it prefers a trans addition.   This becomes very important if you need to halogenate an alkyne to an alkene. Remember that only alkenes can have a cis and trans isomer.

5.   Hydrohalogenation
The addition of a H and a halogen. It is beneficial to add both the H and the halogen in one reagent so one of the binary halogen acids is usually used like HI, HBr, HCl, or HF.

HX can be any halogen acid. (HF, HCl, HBr, HI)
eg.   propene is hydrohalogenated with hydrobromic acid to create 2-bromo-propane


6.  Hydration
This reaction involves the addition of water in the presence of a weak acid. Strong acids tend to draw water away from molecules. Weak acids only stimulate double bonds (Pi bonds) into breaking. Water is ionized slightly in weak acids and can then move into take their proper place in the broken alkene bonds.

eg.  2-methyl-propene is hydrated to 2-methyl-propan-2-ol


7.  Oxidation
The use of cold KMnO4 causes diol (double alcohol) formation.

eg.    but-1-ene is oxidized in buta-1,2-diol


8.   Ozonolysis
Ozonolysis means to cleave or break (to lyse) with oxygen, specifically ozone. There are actually three ways to achieve this type of reaction; with ozone, O3, with Zn and water, and with hot KMnO4.

 You must be very careful about this type of reaction. You are actually taking a single molecule with a single double bond and breaking it up into two new molecules. Depending upon the side chains you can get ketones, aldehydes and carboxylic acids formed as products.
eg. 2-methyl-pent-2-ene is ozonolyed into propan-2-one and propanal

Here is a 2nd possibility  2,3-dimethyl-pent-2-ene is ozonolyed into propan-2-one and butan-2-one



9.  Oxidation of an Alkyne
The term oxidation has many meanings. In organic chemistry oxidation means the addition of oxygen to a molecule. This definition is not the definitive meaning but in the context of this unit it is good enough. The reagent used is a mixture of mercury(II) sulphate and sulphuric acid.

Due to the position of the alkyne bond there is only one product possible in the example below.
eg.   propyne is oxidized into propan-2-one

In the next example there are two possible products above because the position of the alkyne bond in the pent-2-yne molecule. You will have to watch out for this situation. If you go to apply Markinikov's Rule and there are no hydrogens to help you make up your mind then there is probably more than one product.
eg. 2      pent-2-yne is oxidized into penta-3-one and penta-2-one


10.  Ozonolysis of an Alkyne
When an alkyne is subjected to ozonolysis it will always produce two carboxylic acids.

This ozonolysis reaction is identical to the others already demonstrated above. It is the starting material that determines what the products are.
eg.       5-methyl-hepta-3-yne is lysed with hot KMnO4 into 2-methyl-butanoic acid and propanoic acid



Fractional Distillation and Cracking
Read Page 193 - 196
Questions Section 3.3  Page 1 through 6

Activity 3.3 The Great Marble Race
Extension Exercise 3.3 A Fractionation Tower
Self Quiz 3.1 - 3.3
Investigation 3.4 Separating A Mixture by Distillation


Common Functional Groups - Alcohols
The alcohol functional group is an -OH. The polar oxygen gives the molecule properties of solubility with other polar solvents such as water. It's polar properties also cause the molecules to stick together by electrostatic attraction more readily. Ethane is a gas at room temperature whereas ethanol (ethyl alcohol) is a liquid at room temperature.
eg. CH3CH2OH ethanol (ethyl alcohol). 
The parent name is kept and the "e" from ethane was dropped and replaced by "ol". Alcohols are more important than double or triple bonds. If both an alcohol and a double and/or triple bond appear in a molecule then name it as an alcohol. If something more important than alcohol is in a molecule the alcohol gets named as "hydroxy" and a number just like any other attached group.
Go to the Organic Alcohols Worksheet
Demonstration 3.5 Bending Liquids
Extension Exercise 3.5  Functional Groups
Self Quiz 3.4 - 3.6
Extension Exercise 3.7 Comparing Alcohols and Ethers
Extension Exercise 3.7 Naming and Drawing Alcohols

Investigation 3.8 Properties of Alcohols
Ethers     -O-     found only in the interior of two longer chains.
eg. CH3CH2-O-CH3    ethyl methyl ether or methoxy ethane 
   CH3-O-CH3                 dimethyl ether or methoxy methane
 


CH3CH2-O-CH2CH3 diethyl ether or ethoxy ethane 

 
Extension Exercise 3.7 Naming and Drawing Ethers
         
Aldehydes and Ketones

Aldehydes - short form   -COH     or
Aldehydes can only be found on the very end of a molecule at the primary carbon. If you take a close look three of the four bonds on the aldehydes carbon are taken up with the oxygen and the hydrogen. Therefore there is only one bond left for bonding with another carbon and therefore it must be primary.
 Extension Exercise 3.9 Naming and Drawing Aldehydes
example     CH3CH3COH      propanal   or    propyl aldehyde

Be careful about spelling since a simple letter change results in a vastly different molecule. If the aldehyde is not important the group name changes to 'al' with the # of the appropriate parent chain carbon.
 
Ketone - can only be found on the inside of a molecule.
 
Why? As you can see only 2 of the carbon's bonds are used by attachment to the oxygen. Two bonds are available for bonding and to be a ketone these two must be attached to a carbon on each side, hence it must be inside a molecule. But what if one of these bonds is attached to a H? Then its an aldehyde and not a ketone.
 
                       propanone                                                                propanal

The ending "one" is added to the alkane name prefix. If the ketone is not important it's name switches to 'keto' and is treated just like any other substitution group. The ketone is more important than an alcohol and an aldehyde.
Go to Organic Aldehydes and Ketones Worksheet
Extension Exercise 3.9 More Functional Groups
Extension Exercise 3.9 Naming and Drawing Ketones

Safe Use of Solvents
Section 3.10
Read pages 215 - 217
Questions Page 217 1 through 4

Alternative Exercise 3.10 Safety on the Job
 
Carboxylic Acids, Esters, Amines and Amides

Carboxylic Acid  propanoic acid
 
The -COOH group can only exist at the end of a molecule for the same reasons as those of the aldehydes. The root parent name of the above was propane and the "e" is dropped and "oic acid" is added. If you have two -COOH groups in a molecule you have a "dioic acid". There is a three carboxylic acid molecule known. It is known as citric acid in citrus fruits.
 
Extension Exercise 3.11 Naming and Drawing Carboxylic Acids
Activity 3.11 Making Aspirin
Investigation 3.12  Properties of Carboxylic Acids
Self Quiz 3.7 - 3.12

Esters 

Esters can only be found in the interiors of a molecule. An ester is made by dehydration of a water molecule from between an alcohol and a carboxylic acid. When naming the ester molecule the alcohol portion is named first.
 
eg.  methyl ethanoate 
 
Methyl methanoate is made by reacting methyl alcohol or methanol with methanoic acid (old name formic acid). The alcohol label is dropped and the "ic acid" is replaced by "ate". The names are not joined indicating they came from two separate starting molecules.
 
+     ------------>   H2O
 

Examples of some of the more common esters are:

ethyl formate C3H6O2 Fruity, rum-like
ethyl acetate C4H8O2 wine, brandy
ethyl propionate C5H10O2 rum-like
ethyl butyrate C6H12O2 buttery, fruity
ethyl valerate (ethyl pentanoate) C7H14O2 apple
ethyl hexanoate C8H16O2 apple, banana, pineapple
ethyl heptanoate C9H18O2 cognac
ethyl octanate C10H20O2 cognac, apricot
ethyl nonanoate C11H22O2 nutty
ethyl decanoate C12H24O2 cognac, nutty
methyl propionate C4H8O2 rum / black current
methyl butyrate C5H10O2 apple, banana
Extension Exercise 3.13 Naming and Drawing Esters
Extension Exercise 3.13  Artificial Flavours
Activity 3.14  Synthesis of Esters

Amide          eg  . propamide
Amides are found in many biological compounds. They are a major part of amino acids (proteins) and urea (urine).
 
Amine -NH2 without an "O" The key to these compounds is to remember that the N atom has three possible bonds. There are three types of amines based upon these bonding patterns. They are named depending upon the carbon to which they are attached.
 
   1      a primary amine eg. CH3CH2NH2 ethamine or ethyl amine
   2     a secondary amine eg. CH3NHCH3 dimethylamine
  3 a tertiary amine eg.   trimethylamine (the odour that comes from rotting fish).
Go to the Organic Acids and Anhydrides Worksheet
Go to the Organic Esters and Ethers Worksheet
Go to the Organic  Nitrogen Compound Worksheet


Extension Exercise 3.13 Naming and Drawing Amines
Extension Exercise 3.13 Naming and Drawing Amides
Extension Exercise 3.13 Urea and Amino Acids
Extension Exercise 3.15 Further Functional Groups
Extension Exercise 3.15 Functional Groups Review

Self Quiz 3.13 - 3.16
       
Plastic Macromolecules
Macromolecules have molecular masses in the thousands. Each macromolecule is made up of single monomers which are then joined repeatedly over and over.  The joining together of smaller units (monomers) into very large molecules is called polymerization.
 
Nylon 6,6 is made from two molecules "adipyl chloride and hexadiamine"  Nylon is called nylon 6,6 because they join at the 6th carbon in each molecule.
 

                "Adipyl chloride"                                         "Hexadiamine"
These are the monomers
Nylon 6,6
If you look closely you can see the alternating units of 6 carbons, and a nitrogen, repeating endlessly.

neoprene (oil-resistant)


Saran  is made up the the monomer 1,1-dichloro-ethane
1,1-dichloro-ethane      The polymer is below and is called "Saran"


vinyl chloride becomes polyvinyl chloride(PVC)


Acrylnitrile becomes polyacrylnitril (Orlon)


Styrene becomes polystyrene a high impact plastic used in models.


methyl methacrylate (an ester)  becomes polymethyl methacrylate or "plexiglass"


Dacron, a polyester is made from two monomer units.
methyl terephthalate and ethylene glycol  and forms the polyester "Dacron"



Activity 3.17 Classifying Plastics
Extension Exercise 3.18 Natural and Synthetic Polymers

Extension Exercise 3.18 Models of  Polymers
Alternative Exercise 3.19 The Invention of Nylon
Activity 3.20  Making Polymers
Extension Exercise 3.21 Buckyballs
Unit 3 Summary of Structure and Properties


Unit 3 Summary
Unit 3 Review Page 256 - 257  Questions 1 - 17
Unit 3 Self Quiz