Form 4 Chemistry – ORGANIC CHEMISTRY-2

 
 

PREPARATION OF THE ALCOHOL.

Ethanol is commercially produced using a process called fermentation. Many other alcohols can be made this way, but are more likely to be produced by synthetic routes – from natural gas, oil or coal.

Fermentation is the process in which yeast breaks down sugar into alcohol and carbon dioxide. Yeast is tiny. The process does not need oxygen, hence it is the form of anaerobic respiration.

These are two types of fermentation

a) Alcoholic fermentation – producing alcohol

b) Lactic acid fermentation – producing lactic acid

The word equation for this process is:

Carbon dioxide gas bubbles out of the fermenting solution into the air leaving a mixture of ethanol and water. It’s important that no air is present or the yeast will produce ethanoic acid – the chemical found in vinegar.  

Beer and lagers
Barley, hops, water and live yeast produce beers and lagers. The sugar in the mix comes from the spouting barley. Bitter, stout and ale use top-fermenting yeast, while lager uses a variety that sinks to the bottom.    

Wine In wine making the sugars come from the flesh of the crushed grapes. The type of wine produced depends on the type of grape used in the process.    

Spirits and distillation

Yeast cannot survive in high levels of alcohol, so to create stronger spirits an additional process, distillation, is required. Fermented drinks are distilled to create vodka, rum and other spirits. Distillation relies on ethanol having a lower boiling point than water. When the fermented drink is heated the ethanol vaporizes at 78.5 degrees and the water is left behind (water boils or vaporizes at 100 degrees). The ethanol gas is caught and cooled so it condenses into a stronger concentration of ethanol liquid.    

Alcohol can be prepared locally or in the industries

1. Local preparation of the alcohol; raw material – sugar beet, cereals such as (cassava, millet, maize)

b) Industrial preparation of the alcohol; Raw material – maltose sugar – C₁₂H₂₂O₁₁

The enzyme known as the diastase help to covert the starch to maltose; normally the starch containing food are crushed then treated with the steam to extract starch from them. The malt from Barley added in order to convert the starch to maltose, the mixture allowed to stay for about one hour also yeast can be added, and the yeast contains two enzymes maltose and zymase.

Definition: Fractional distillation – is the process used to separate the components of the homogeneous mixtures which differ in the boiling points 9BP) consider the diagram below

        
         

Where

A – Stand for ethanol – C₂H₅OH                                                 K- Round bottomed flask

B – Cold water to distillate ethanol vapors to liquid                       A₁– Ethanol(C2H5OH)

C – Ethanol (78⁰c) and water (100⁰c)                                         A₀-Beaker(Container)

D – Ethanol vapour

E – Ethanol drops

F – Thermometer record temperature

G – Stand and clump

H – Cork

I – Condenser

Note

1. The mixture boiled until temperature reach about 80 – 85⁰c then stopped at this point all ethanol become extracted from the mother solution
   
2. The yeast cells are killed by the high temperature
   
3. The yeast contains two enzymes known as Maltose, and Zymase
   
4. Alcohol can  also prepared from the sugar cane
   

   E.g. sugar cane + water yeast  →  Glucose + Fructose
   

   Sucrose + water  → Glucose + Fructose
   

   C₁₂H₂₂O₁₁ + H₂O →  CH₁₂O₆ + C₆H₂O₆
   

   The invertase enzymes connect sucrose to glucose and fructose
   

    
    

   PROPERTIES OF THE ALCOHOL
   

   The following are the properties of the Alcohol
   

   1. It is colorless and has odour taste
   

   2. It is soluble in water and can from the homogeneous mixture water
   

   3. It boils at 78^oc
   

   4. Purely ethanol is non – electrolyte
   

    
    

   REACTION IN ALCOHOL
   

   They includes
   

   1.    Reaction with Carboxylic Acid
   

   
   

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• Alcohol reacts with carboxylic acid to form “Ester” and water, hence reaction called Esterification reaction
  
• Example
  

      
  

  2. Reaction with Electropositive metals
  

  E.g. Alcohol + Electropositive metals   salt + hydrogen
  

  Examples
  

  Ethanol + sodium  →  sodiumethoxide + hydrogen
  

  C₂H₅OH + Na →  C₂H₅ONa + H₂O
  

  Ethanol + Potassium →  potassiumethoxide + hydrogen
  

  C₂H₅OH + K → C₂H₅OK + H₂
  

   
   

  3. Oxidizing agent reaction e.g. potassium permanganate – KmnO₄ or (O)
  

  E.g. Alcohol + oxidizing agent →  Carboxylic acid
  

  Example
  

  Ethanol + (O)  → Ethanoic acid
  

  C₂H₅OH + (O) → CH₃COOH
  

   
   

  4. Reaction with concentrated sulphuric acid Con. H₂SO₄ at 180⁰c/ 140⁰c
  

  Example
  

   
  

  In this reaction acid acts or behave as dehydrating since removed water from the Alcohol
  

  
  

   
   

  5.  Reaction with PCl₅, PCl₃, SOCl₂
  

  E.g.      ROH + PCl₅ → RCl + POCl₃ + HCl
  

              C₂H₅OH + PCl₅ → C₂H₅Cl + pOCl₃ + HCl
  

              ROH + PCl₃ → RCl + H₃PO₄ + HCl
  

              C₂H₅OH +PCl₃ → C₂H₅Cl + H₃PO₄ + HCl
  

              ROH + SOCl₂ → RCl + SO₄ + HCl
  

              C₂H₅OH + SOCl₂ → C₂H₅Cl + SO₂ + HCl
  

   
   

  Where
  

  PCl₅ – phosphorus pentachloride, PCl3 – phosphorus trichloride
  

  SOCl₂ – sulphuric trichloride or vinyl chloride
  

  Note
  

  
  

   
   

  COMMERCIAL USES OF ETHANOL – C₂H₅OH
  

  • Manufacture of the spirit (purely spirit) which can be used in the hospital for the injections or saloon after shaving the spirit is used in order to kill the bacteria (sterilization). E.g. Methanol (5%) extracted by the dry distillation of the wood mixed with 95%- ethanol then we obtain methylated spirit which is coloured before being sold to the public this is to avoid the ethanol from being consumed as the drink.
    
  • They can be used for
    

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• Preservation of the specimen and food
  
• Fuel and light
  
• Varnishes, polishes, paint making and removing
  
• Temporary solvent in the manufacture of the soap, medicine, also to precipitate the chemicals from their aqueous solutions
  
• Raw materials for the manufacture of the chemical such as trichloromethane and ethane
  

  3.   Manufacture of the Alcoholic drinks egg beer contains 2 – 6% ethanol, made by fermenting mash barley. Wines are made grapes, and yeast for the fermentation grows on the skin of the grapes. Wines contains 10% ethanol
  

  Note: sugar beet molasses – Are the remains of sugarcane
  

   
   

  HARMFUL EFFECT OF ALCOHOL
  

        Alcohols have much harmful effects to the body, if taken as a drink. However, the effect of a given amount of ethanol depends on the rate of drinking, the size of the drinker, the alcoholic content of the drink, health and diet of the drinker and other factors.
  

           The noticeable harmful effects of alcohols including:
  

  1)      Heavy drinking of alcohol causes shrinkage of the brain cells, reduces power of abstract reasoning and destroys liver cells.
  

  2)      Heavy drinking can cause cancer of the liver, stomach and gullet.
  

  3)      Heavy drinking can upset digestion and reduce blood cell formation thus causing anaemia.
  

  4)      Some of car accidents by drivers is due to heavy alcohol drinking. Don’t drink and drive.
  

  5)      Alcohol drinking can be one of the sources of family conflicts, misunderstandings, misuse of money and even divorce.
  

  6)      Methanol(methyl alcohol) is quite toxic. Ingestion of as little as 30ml can cause permanent blindness or death.
  

  CARBOXYLIC ACID
  

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A carboxylic acid is an organic compound that contains a carboxyl group (C(O)OH). The general formula of a carboxylic acid is R-C(O)OH with R referring to the rest of the (possibly quite large) molecule. Carboxylic acids occur widely, and include the amino acids and acetic acid (active ingredient in vinegar).

The general formula  

                                                                                                       

Where

R = CH₃ or C₂H₅ = alky group

Example

R = CH₃ = CH₃COOH

R = C₂H₅ = C₂H₅COOH

Note: Function Group – COOH of carboxylic acid can’t move from the first or last carbon ( c ) atom, this mean functional group is fixed but that of alcohol can move

       
 

CARBOXYLIC ACID

Carboxylic acids are organic acids that are characterized by R-COOH group. The R is an alkyl group. The functional group is

Organic acids have the general formula 

Where n = 1, 2, 3, . . . . 

From the general formula the first five members of homologous series are shown in table below.

                                              Homologous series of carboxylic acid.

 
NB It seems that homologous series of carboxylic acid that the carboxylic acid can be represented by using the general molecular formula of  . 

     where  n = number of carbon atoms in the compound.

STRUCTURAL FORMULA OF SOME CARBOXYLIC ACIDS
Condensed and open structural formula of carboxylic acid.

 

NOMENCLATURE OF CARBOXYLIC ACIDS

In naming carboxylic acids, all rules of naming alkenes are used except the modifications that follows:

(i) The suffix ‘e” of alkanes is replaced by suffix ‘oic” of carboxylic acid.

eg; Alkane                                  Carboxylic acid

1. Methane                          -Methanoic acid
2. Ethane                             -Ethanoic acid
3. Propane                           -Propanoic acid 

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 (ii)  The longest chain of carboxylic acid must includes the carboxylic group

must includes the carboxylic group

             

            eg:  (i) CH₃CH₂CH₂CH₂COOH – Pentanoic acid

                   (ii)CH₃CH₂COOH – Propanoic acid        

(iii)  If the substituent groups are attached to the parental chain of the Carboxylic acid, their position must be indicated.  Numbering starts the side where by carboxylic group (COOH) is early attached.

 
 

 eg:                                           4,4,4 – Trichlonobutanoic acid

  
 

R-5.7.1.2 Substituted carboxylic acids

Hydroxy, alkoxy, and oxo acids. Some trivial names for hydroxyl and alkoxy acids are retained. The names of carboxylic acids containing an aldehydic group attached to, or a ketonic group contained in the principal chain or parent ring system, are generally derived from the names of the corresponding simple carboxylic acids by adding prefixes such as “oxo-“, “dioxo-“, etc., denoting =O substituents, or “formyl-“, demoting a -CHO substituent.

Example

   

The carboxylic acid also has common which people they know due to daily uses of such carboxylic acid

       

Give the IUPAC names of the following compounds

  

IUPAC name: 2, 3 – dibromobutanoic acid

                              

IUPAC name

2 – Chloro, 4, 5 – dimethylhexanoic acid

iii)       

Name

2,2 – dimethylpropanoic acid  

PROPERTIES OF THE CARBOXYLIC ACID

• They are Acidic in nature so they can react with base then form salt and water
  
• They have carboxylic group as their functional group – COOH
  
• They end up with suffix – “oic”
  

  E.g. Methanoic, Ethanoic
  

  Where
  

  n = 0…..methanoic
  

  n = 1…..ethanoic
  

  n = 3, 4, 5, 6, 7….10
  

  C_nH₂nO₂ where n = 1, 2, 3, 4,
  

   
   

  REACTION OF CARBOXYLIC ACID – C00H
  

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Carboxylic acid are acidic in nature so they can react with base then form salt and water as other acid (mineral acid)

1. CARBOXYLIC ACID AND BASE (Alkali)
   

   E.g. Acid + base  → salt + water
   

   Example
   

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• Ethanoic + sodium → sodium + water
  

     Acid     hydroxide →   Ethanoate
  

              CH₃COOH + NaOH  → CH₃COOHNa + H₂O
  

• Acetic acid + sodium hydroxide  → Sodium Acetate   + Water         
  

            CH₃COOH + NaOH       →  CH₃COONa + H2O 
  

• Formic Acid + potassium hydroxide   →  Potassium methanoate +   water
  

                HCOH + KOH         →    HCOOK + H₂                                                                                                                                                                                                                                                                                                                                               
  

  2. CARBOXYLIC ACID AND METAL (K, Na)
  

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            Acid + metal   → Salt + hydrogen

Example

Acetic Acid + sodium   →  Sodium Acetate + Hydrogen

            CH₃COOH + Na     →  CH₃COOHNa + H₂

            CH₃COOH + K      →   CH₃COOK + H₂

 
 

ESTERIFICATION AND NEUTRALIZATION

ESTERIFICATION – Is the reaction between the Alcohol and carboxylic acid under control of concentrated sulphuric acid (H₂SO₄) and heat (Δ)

     

Acid provide – H- which shift equilibrium position than ester produced

 
 

CONDITION FOR ESTERIFICATION

They include

1.  Concentrated sulphuric acid (H₂SO₄) as catalyst. The concentrated sulphuric acid is used as the catalyst to speed up the rate of the chemical reaction.
   
2. Heat.
   

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PRODUCTS OF ESTERIFICATION

They include

1. Ester
   
2. water
   

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ESTER – Are the organic compounds with the smell (sweet smell) like fruits and have structure

Example

    

NEUTRALIZATION

This is the reaction between acid and base (Alkali) to form salt and water

Acid + Base  → salt + water

• Esterification and neutralization have differences as shown below.
  

   
   

  DIFFERENCE BETWEEN ESTERIFICATION AND NEUTRALIZATION
  

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DIFFERENCES BETWEEN ALCOHOL AND CARBOXYLIC ACID

 
 

SAPONIFICATIONS

Saponification is a process that produces soap, usually from fats and lye. It involves a reaction between a base, usually sodium hydroxide (caustic soda), and an ester group on a compound. Triglycerides are an example, which is an ester of a fatty acid. The triglycerides are hydrolyzed to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes produce glycerol. “Saponifiable substances” are those that can be converted into soap

      

APPLICATION OF THE SAPONIFICATION

The knowledge of the saponification is applied in the industries to manufacture soap , Ester such as oil is mixed with the base then salt hence heated (boiled), then soap particles precipitates to form the down ward (boiled), then soap particles.