Organic Compounds PDF

**[Some Families of Organic Compounds]** **[Tetrahedral Compounds]** A tetrahedral carbon is a carbon atom which has tetrahedral geometry. This geometry happens only when the carbon atom has 4 single bonds. \*\*Definition: A chloroalkane is a compound in which one or more of the hydrogen atoms in...

**[Some Families of Organic Compounds]** **[Tetrahedral Compounds]** A tetrahedral carbon is a carbon atom which has tetrahedral geometry. This geometry happens only when the carbon atom has 4 single bonds. \*\*Definition: A chloroalkane is a compound in which one or more of the hydrogen atoms in an alkane molecule have been replaced by chlorine atoms.\*\* Monochloromethane Dichloromethane Trichloromethane Tetrachloromethane\ (chloroform) Chloroalkanes are used as solvents for removing oil and grease marks from machinery and in dry cleaning of clothes\ - Chloroalkanes are weakly polar -They are not soluble in water\ - They are soluble in non-polar solvents (cyclohexane)\ - Liquids at room temperature. [Alcohols] \*\*Definition: A functional alcohol is an atom or group of atoms which is responsible for the characteristic properties of an organic compound or a series of organic compounds.\*\* Alcohols may be imagined as derived from alkanes by replacing a H atom by an -OH group. The -OH is called the hydroxyl or hydroxide group and is the functional group in alcohols. General formula of alcohols = C~n~H~2n+1~OH\ Named by changing the -e in alkanes to -ol. \*\*Definition: A primary alcohol is one where the carbon atom attached to the -OH group is attached to only one other carbon atom\*\*\ \ Ethanol \*\*Definition: A secondary alcohol is one where the carbon atom joined to the -OH group is attached to two other carbon atoms.\*\*\ \ Propan-2-ol \*\*Definition: A tertiary alcohol is one where the carbon atom joined to the -OH group is attached to three other carbon atoms\*\*\ \ 2-methylpropan-2-ol \- Ethanol (C~2~H~5~OH) is the most common and best known alcohol. It is found in alcoholic drinks.\ - It is made by fermenting glucose using yeast:\ C~6~H~12~O~6~ → 2C~2~H~5~OH + 2CO~2~\ - To prevent people from drinking industrial ethanol, methanol is added, as it is particularly toxic. This ethanol is now denatured and is called methylated spirits. \- Alcohols have higher boiling points than their corresponding alkanes. This is due to hydrogen bonding between the alcohol molecules.\ - Small alcohol molecules are soluble in water due to the hydrogen bonding between the molecules.\ - Larger alcohol molecules (e.g., butanol) are not soluble in water as the effect of the hydrogen bonding decreases as the molecule gets bigger.\ - These larger alcohols are soluble in non-polar solvents like cyclohexane [Planar Compounds] A planar carbon is a carbon atom which has planar geometry. This geometry happens only when the carbon atom is unsaturated (contains a double- or triple-bond). [Aldehydes\ ]Aldehydes form a homologous series of organic compounds containing the\ -CHO functional group.\ - Named from the parent alkane by changing the -e to -al.\ - Have dipole-dipole interatcions between molecules because of the polar carbonyl group\ - Boiling points are higher than their respective alkanes due to the dipole-dipole forces\ - Boiling points are lower than their respective alcohols as alcohols have hydrogen bonds\ - Small aldehydes are soluble in water due to the polar carbonyl group Methanal 2-methylpropanal Benzaldehyde [Ketones] Ketones form a homologous series of organic compounds containing the \>C=O functional group\ - Named by changing the final -e of the parent alkane to -one\ - The highly polar C=O carbonyl group is always located on one of the central carbons, and never at the end of the carbon chain in a ketone.\ - Boiling points are higher than their respective alkanes due to the dipole-dipole forces\ - Boiling points are lower than their respective alcohols as alcohols have hydrogen bonds\ - Small Ketones are soluble in water due to the polar carbonyl group\ - Used as solvents (Acetone -- Removes nail varnish) Propanone Butanone [Carboxylic Acids] Carboxylic Acids are a family of organic compounds that contain the carboxyl group -- COOH and have the formula C~n~H~2n+1~COOH\ - Named by changing the final -e of the parent alkane to -oic acid\ - The highly polar C=O carbonyl group is always located at the end of the carbon chain in a carboxylic acid\ - Boiling points are higher than their respective alkanes, alcohols, aldehydes and ketones due to the relatively strong hydrogen bonds between the carboxylic acid molecules\ - Small carboxylic acid molecules are soluble in water due to the Hydrogen Bonding\ - The longer the carbon chain becomes, the less soluble the carboxylic acid is in water, as the effect of the polar -OH group decreases\ - Propanoic acid prevents mould and is used as a food preservative\ - Benzoic acid is used in antiseptic medicines\ - Ethanoic acid is vinegar Methanoic Acid Butanoic acid [Esters] Esters are a family of compounds with general formula RCOOR' and a functional group -COO-.\ - Derived from carboxylic acids by replacing the H of the -OH group with an alkyl group\ - Prepared by the reaction between an alcohol and a carboxylic acid Ethanoic Acid Methanol Methyl Ethanoate An esterification reaction is an example of a condensation reaction \*\*Definition: A condensation reaction is a chemical reaction in which two molecules combine to form a larger molecule with the loss of a smaller molecule such as water.\*\* \- To name an ester we must divide the structure by identifying the part derived from the carboxylic acid and the part derived from the alcohol\ - Name the alcohol-derived section first e.g., methyl, ethyl\ - Identify the carboxylic acid\ - Remove "-oic acid" from the name and replace it with "-oate"\ - Combine the name from step 2 with the name from step 3. \- The polar carbonyl group (C=O) means that ester molecules have Dipole-Dipole intermolecular forces\ - Small ester molecules are soluble in water due to the Dipole-Dipole intermolecular force\ - Used to give fruity flavourings to food\ - Used in the manufacture of perfumes and cosmetics **[Bonding in Benzene. Aromatic Compounds]** \- Each Carbon atom in the benzene ring has four electrons in its outer shell\ - Each carbon atom uses three of these electrons to form sigma bonds by head-on overlap of atomic orbitals\ - Two of these sigma bonds are formed between each carbon atom and two adjacent carbon atoms\ - The third sigma bond is formed with an atom of hydrogen\ - Each remaining valence electron (6) is shared between all 6 carbons\ - These delocalised electrons give extra stability to the benzene molecule\ - Bond lengths between all carbon atoms are equal **[Organic Natural Products]** Many organic compounds are found to occur in nature Ibuprofen Vanillin\ (lab made) (lab made) Eugenol Menthol\ (Natural) (Natural) **[Mandatory Experiment: To extract clove oil from cloves by steam distillation ]** Diagram of a science experiment Description automatically generated**[(1)]** 1. Set up the Quickfit apparatus as above 2. Note the mass of the cloves, and place them in the pear-shaped flask. Cover with a little warm water (about 5 cm^3^). 3. Place an adequate supply of water in the steam generator, connect it to the rest of the apparatus and set it to boil. If Quickfit apparatus is used for steam generation make sure that you use anti-bumping granules in the steam generator. 4. If the level of the boiling water in the steam generator falls too low, the system will not work smoothly. Remove the heat, carefully loosen the safety valve, and top up the steam generator with **hot** water. Reconnect everything and resume heating. 5. Collect the distillate. It should have a pale milky appearance. Using the dropping funnel as a receiver at this point will facilitate the next stage of the separation. 6. After 20 to 30 minutes disconnect the steam generator to avoid the possibility of suck-back problems and turn off the heat under it. You will have probably collected between 40 and 50 cm^3^ of distillate. Note the smell of the distillate. \*\*Definition: A steam distillation is a separation process used to isolate compounds at temperatures below their composition temperatures. It is carried out by bubbling steam through the material and distilling off the immiscible liquids.\*\* \*\*An emulsion is a dispersion of small droplets of one liquid in another liquid in which it is not soluble.\*\* **[To isolate clove oil (eugenol) from an emulsion of clove oil and water by liquid-liquid extraction using cyclohexane]** 1. Disconnect the dropping funnel from the rest of the apparatus. 2. Add about 8 cm^3^ of cyclohexane to the distillate in the dropping funnel. 3. Stopper the dropping funnel and shake the mixture. Release any pressure build-up carefully after each shake by inverting the dropping funnel while holding the stopper and slowly opening and shutting the tap. 4. Run the lower aqueous layer off. Collect the top layer - this contains the clove oil and the cyclohexane. 5. Dry the organic layer by shaking with anhydrous sodium sulfate in a conical flask. If possible, allow to stand overnight, before removing the solid by filtration or decanting. 6. Separate the more volatile cyclohexane from the clove oil by placing the mixture in a small beaker (whose mass is known) on a water-bath in a fume cupboard. The cyclohexane evaporates, leaving the clove oil behind. (Note that if the cyclohexane is to be distilled off it will boil at 81 ^0^C.) Prepare the students for a very low yield of clove oil. 7. Note the smell of the clove oil. Do not allow the clove oil to come in contact with your skin **[(2)]** \- A small quantity of an oily substance is left in the conical flask\ - The oily substance has a strong smell of cloves **[Exam Questions]** [2012 -- HL -- Section B -- Question 8] 8\. Study the reaction scheme and answer the questions that follow. A diagram of a flowchart Description automatically generated \(a) Give the systematic (IUPAC) name for (i) the alcohol A, Propan-2-ol(ii) the ester B. Propyl methanoate\ (b) Alcohol A and propan-1-ol are structural isomers. Explain the underlined term.\ Compounds with the same molecular formula but different structural formula\ What is the structural difference between a primary alcohol and a secondary alcohol?\ Primary: One carbon attached to OH carbon.\ Secondary: Two carbons attached to OH carbon.\ Identify another pair of structural isomers from the reaction scheme. Propanal and propanone\ (c) Identify a compound in the scheme whose carbon atoms are all in tetrahedral geometry. A -- propan-2-ol.\ (d) Name the reagent and catalyst used to bring about the conversions labelled R. Regent: Hydrogen.\ Catalyst: Nickel\ (e) Propanal is oxidised by Fehling's reagent. Describe how this reaction is carried out.\ - Mix equal amounts of Fehling's A and Fehling's B in a test tube.\ - Add small amount of propanal.\ - Heat in water bath.\ - Red precipitate formed.\ Why does propanone not react with Fehling's reagent?\ Propanone is not easily oxidised\ (f) Which compound in the scheme would you expect to have a fruity odour?\ B -- propyl methanoate **[References]** 1. Examlearn.ie 2. Examlearn.ie