Carboxylic acids.pptx ,short notes for organic chemistry

short notes for organic chemistry

1. Carboxylic acids Carboxylic acids are a homologous series of carbon compound which contains carboxyl (-COOH) group. Eg . , methanoic acid ( formic acid), ethanoic acid ( acetic acid ) Household substance , vinegar , is an aqueous solution containing ethanoic acid. Carboxylic acids are formed by oxidation of the corresponding alcohols ( ethanol to ethanoic acid)

2. Acidic properties of the carboxylic acids Ethanoic acid and other carboxylic acids are weak acid a pH of 3-5 depending on the concentration of the solution. Reaction with metals They have the same reaction as other acids ( HCl , H2SO4) but slower reaction ( produce (-ate) salt and hydrogen). Carboxylic acid and –ate ( magnesium ethanoate is a salt) Reaction with carbonates Carbonates react with acids to give a salt , carbon dioxide and water . sodium ethanoate , calcium ethanoate ( colourless solution)  

3. Esters Esters are a homologous series of carbon compounds which contains carboalkoxyl ( -COO- ) group. Alcohol + carboxylic acid esters e.g. ethyl ethanoate ( used as solvent in nail polish and nail polish remover )  

4. This reaction is called esterification or condensation ( H and O condenses to form H2O) This reaction is reversible Drawing and naming esters Draw OH groups next to each other Remove H2O ( H from alcohol ( - yl ) and OH from ethanoic acid( - oate ) C=O containing part ( - oate )

5. Reverse the reaction Uses of esters Esters have a sweet , fruity smell Ethyl ethanoate – used in solvent Other esters – used in food flavoring and perfumes Esters are volatile liquids with distinctive smells.

6. Making and testing esters Put 1 cm3 of ethanoic acid and 1 cm3 of ethanol into a boiling tube . Mix well and carefully add a few drops of concentrated sulfuric acid . Place the boiling tube in a beaker of hot water at about 80 ˚C for 5 minutes . Allow the contents of the tube to cool and then pour the mixture into a beaker half-full of 0.5 mol /dm3 sodium carbonate solution ( excess acid reacts with the metal carbonate to smell the ester better) The acid and alcohol will mostly dissolve in the water , but the ester won’t . A layer of ester will separate and float on top of the water. Smell the product by gentle wafting the odor towards your nose with your hand. Repeat this procedure for the other combinations of acids and alcohols. Butyl butanoate ( pineapple) , propyl ethanoate ( pear)

7. Synthetic polymers Polymerization Polymerization is the joining up of lots of little molecules ( monomers ) to make one big molecule( polymer) Addition polymerization Molecules simply add onto each other without anything else being formed. Polymerization of ethene Ethene is the smallest alkene Polymerization of ethene poly ethene or polythene Chain length 4000 – 40000 carbon atoms Uses of ethene Low density poly ethene ( LDPE) very flexible and not strong ( plastic bags) High density poly ethene ( HDPE) greater strength and rigidity ( plastic bottles)  

8. Polymerization of propene Propene is a three carbon alkene containing double bond Polymerization of propene poly propene or propylene Uses of poly propene Stronger than poly ethene to make ropes and crates. Polymerization of chloroethene Chlorothene ( CH2= CHCl ) also called vinyl chloride Ploymerization of chloroethene poly chloroethene or polyvinylchloride [PVC] Uses of poly chloroethene Quite strong and rigid – water pipes and replacement windows Flexible by adding plasticizers – sheet floor covering , clothing No electricity conduction – used for electrical insulation.  

9. Polymerization of tetrafluroethene Tetrafluoroethene – all H are replaced by fluorine ( CF2= CF2) Polymerization of tetrafluroethene – poly ( tetrafluoroethene ) [PTFE] or Teflon Uses of poly tetrafluoroethene Very unreactive due to the strong carbon –fluorine bonds Non-stick coating for pots and pans Lining containers for corrosive chemicals. Working out the monomers for a given additional polymers From the given structure of a polymers ,to deduce the monomer 1. Take any repeat carbon atoms 2. Replace C-C with C=C 3. Get rid of continuous bonds

10. Disposable of additional polymers Dispose ( bury ) them in landfill sites – unchanged for thousand of years in big holes Incinerate ( burn ) plastics – used for electricity from heat produced but CO2 production will cause global warming. How to solve ? Recycling of plastics To save the raw materials It takes very long time to break them ( polyethene , polychloroethene ) down in the environment as they contain strong covalent bonds and non- biodegradble . Advantages and disadvantages for using either method to dispose of plastics

11. Condensation polymerization Making a polyester In additional polymerization – nothing is lost In making a polyester – small molecule ( H2O or HCl ) is lost The elimination of water gives the name condensation polymerization .

12. The monomers Two monomers combine One monomer is diol [two alcohol (-OH) functional group at both ends ]. Other monomer is dicarboxylic acid [two carboxyl group –COOH at both ends ].

13. Forming a polyester Diol and dicarboxylic molecules join together with loss of a water molecule. Biodegradable polyesters Polyester is biodegradable ( takes hundred of years ) , called bio-polyesters , due to more reactive ester linkage. Can be made from lactic acids , known as 2-hydroxypropanoic acid( polylactic acids), self-polymerize PLA can be used – biodegradable plastic bags - internal stitches in surgery