13.-ALCOHOLS and its functional gro.pptx
- 1. CLAIRE N. MONGCAL, LPT ALCOHOLS (ORGANIC CHEMISTRY)
- 4. WHAT IS ALCOHOL? Alcohols are the organic compounds in which a hydrogen atom or an aliphatic carbon is replaced with the hydroxyl group. Thus an alcohol molecule consists of two parts; one containing the alkyl group and the other containing the hydroxyl group. They have a sweet odor. They exhibit a unique set of physical and chemical properties. These physical and chemical properties of alcohols are mainly due to the presence of hydroxyl group. The alcohol structure depends on various factors.
- 5. Properties of alcohol can be explained by the following points – Alcohols are colorless. They generally give a sweet smell except for glycerol and a few lower alcohols. They are flammable and produce a blue flame. They don’t produce any smoke while burning. They are generally liquid at room temperature. Although glycerol is a viscous liquid.
- 6. Boiling Point of Alcohol - They generally have higher boiling points if we compare them with other hydrocarbons. For example, ethanol shows a boiling point of 78.29℃ while hexane shows a boiling point of 69℃. This is because of the presence of intermolecular hydrogen bonding between hydroxyl groups of alcohols. The boiling point of alcohol increases with an increasing number of carbon atoms in organic alcoholic compounds. Alcohols work as suitable solvents for many organic compounds as organic compounds are insoluble in water.
- 7. Alcohols are acidic in nature. They react with metals such as sodium, potassium etc. It is due to the polarity of the bond between a hydrogen atom and the oxygen atom of the hydroxyl group. Primary alcohols are more acidic than secondary and tertiary alcohols. Due to the polar -OH bond in alcohols, they are more soluble in water than other simple hydrocarbons. For example, methanol and ethanol are miscible in water.
- 9. Alcohol structure is mainly attributed to the presence of the hydroxyl group. In alcohols, the carbon atom of the main chain is bonded to the oxygen atom of the hydroxyl group by a sigma (σ) bond. This sigma bond is formed due to the overlap of an sp3 hybridized orbital of carbon with an sp3 hybridized orbital of oxygen. Due to the repulsion between the unshared electron pairs of oxygen, the bond angle of C-O-H bonds in alcohols is slightly less than the tetrahedral angle (109°-28′).
- 10. Alcohols are considered to be as the derivatives of water where one among the hydrogen atoms are replaced by alkyl group, which is typically represented by the letter R in an organic structure. Alcohol also comes in different structures and forms. Alcohols are known to be one among most of the commonly occurring organic compounds. These are utilized in the form of sweeteners, preparation of perfumes, and sometimes in the process of synthesizing other compounds, wherein some others are abundantly manufactured in organic chemicals coming in various industries.
- 11. Alcohols are differentiated based upon the presence of the hydroxyl group attached. The location of this hydroxyl group as well will change the physical and chemical properties of any alcohol. Classification of alcohol based on the number of OH present. 1. Monohydric alcohols- contains one OH group. (CnH2nOH ) Example: CH3CH2OH 2. Dihydric alcohols- contains 2 OH group. (CnH2n(OH)2) Example: CH2-OH CH2-OH Main Types of Alcohols ETHANO L ETHYLENE GLYCOL
- 12. 3.Trihydric alcohols- contains 3 OH group. ( (CH2)n(OH)3 ) Example: 4. Polyhydric alcohols- contains many OH group. Example: GLYCEROL GLUCOSE
- 13. There are three types of alcohol based on the number of carbons (Monohydric). Alcohols are classified as primary, secondary or tertiary alcohols.
- 14. The classification is done in accordance with the carbon atom of an alkyl group is attached to the hydroxyl group. Most of the alcohols are known to be colorless liquids or even are said to behave as solid at room temperatures. Alcohols with less molecular weight are said to be highly soluble in water; and with their increase in molecular weight, they tend to become less soluble and their vapor pressures, boiling points, densities, and the viscosities to increase.
- 15. Let us study in brief about the types of monohydric alcohols. 1. Primary Alcohols Primary alcohols are those alcohols where the carbon atom of the hydroxyl group (OH) is attached to only one single alkyl group. Some examples of these primary alcohols include Methanol (propanol), ethanol, etc. The complexity of this alkyl chain is unrelated to the classification of any alcohol considered as primary. The existence of only one linkage among –OH group and an alkyl group and the thing that qualifies any alcohol as a primary. (RCH2OH)
- 16. 2. Secondary Alcohols Secondary alcohols are those where the carbon atom of the hydroxyl group is attached to two alkyl groups on either side. The two alkyl groups present may be either structurally identical or even different. Some examples of secondary alcohols are given below. (R2CHOH)
- 17. 3. Tertiary Alcohols Tertiary alcohols are those which feature a hydroxyl group attached to the carbon atom which is connected to 3- alkyl groups. The physical properties of these alcohols mainly depend on their structure. The presence of this -OH group allows the alcohols in the formation of hydrogen bonds with their neighboring atoms. The bonds formed are weak, and this bond makes the boiling points of alcohols higher than its alkanes. (R3CHOH ) Examples of tertiary alcohols include-
- 19. As with other types of organic compounds, alcohols are named by both formal and common systems. The most generally applicable system is that adopted at a meeting of the International Union of Pure and Applied Chemist ry (IUPAC) in Paris in 1957. Using the IUPAC system, the name for an alcohol uses the -ol suffix with the name of the parent alkane, together with a number to give the location of the hydroxyl group. The rules are summarized in a three-step procedure:
- 20. 1.The longest continuous chain (LCC) of carbon atoms containing the OH group is taken as the parent compound -- an alkane with the same number of carbon atoms. The chain is numbered from the end nearest the OH group. 2.The number that indicates the position of the OH group is prefixed to the name of the parent hydrocarbon, and the -e ending of the parent alkane is replaced by the suffix -ol. (In cyclic alcohols, the carbon atom bearing the OH group is designated C1, but the 1 is not used in the name.) Substituents are named and numbered as in alkanes. 3.If more than one OH group appears in the same molecule (polyhydroxy alcohols), suffixes such as -diol and -triol are used. In these cases, the -e ending of the parent alkane is retained.
- 26. Oxidation Reaction of Alcohol – Alcohols produce aldehydes and ketones on oxidation. The reaction is given below – C₂H₅OH + 2O CH₃COOH + H₂O Ethanol Ethanoic acid Combustion of Alcohol – On heating ethanol gives carbon dioxide and water and burns with a blue flame. The reaction is given below – C₂H₅OH + 3O₂ 2CO₂ + 3H₂O → →
- 27. Dehydration of Alcohol – Alcohol can be dehydrated in an acidic medium. The removal of water molecules from a compound is called dehydration. Upon dehydration of alcohol alkenes are produced. The reaction is given below – C2H5OH (conc. H₂SO₄,▵)→C₂H₄ + H₂O The reaction of Alcohol With Metal – Due to its acidic nature alcohol reacts with metal and forms alkoxide. For example, when ethanol reacts with sodium forms sodium ethoxide and hydrogen gas. The reaction is given below – 2C₂H₅OH + 2Na →2C₂H₅ONa + H₂
- 28. Formation of Halides From Alcohols – Alcohol reacts with HCl and forms alkyl halides by removal of hydroxyl groups. The reaction is given below ROH + HCl (Zn) → R-Cl + H₂ Esterification – Alcohol reacts with a carboxylic acid in presence of a catalyst and forms ester. It is called Fischer esterification. The reaction is given below – C₂H₅OH + C₂H5COOH →C₄H₈O₂ + H₂O
- 31. Alcohols are consumed as beverages where the alcohols specifically consist of 30–40 per cent of ethanol by volume. These are used as an anti-freezing agent with a mixture of a solution containing ethylene glycol dissolved in water. Alcohol ethanol is used as an antiseptic agent. Some alcohols are used as fuels in internal combustion engines like the methanol. In the field of medicine, a few of them are used as preservatives for the specimens in laboratories. Uses of Alcohols
- 32. 06 ACTIVITY
- 34. 1.What is alcohol? 2.What are the different types of alcohols? 3.Differentiate Monohydric, Dihydric, Trihydric and Polyhydric. 4.Differentiate Primary, Secondary and Tertiary alcohols. 5.What are the uses of alcohol?
- 35. THANK YOU!