Alcohol in organic chemistry

Alcohol with its structures, physioochemical properties and preparation

1. Alcohol “Their Structures, Physiochemical Properties and Preparation” Saad Anwar Microbiologist Topic:

2. Structure and Physical Properties ALCOHOL An organic compound containing a hydroxyl group attached to an alkyl group. a non-polar (alkane-like) chain. a polar hydroxyl group. Alcohols have the general formula: R-OH, where “R” involves a saturated C-atom (bound to hydrogen's and/or other carbons). For example:

3. Classification of alcohols Alcohols may be classified as 1 o (Primary), 2 o (Secondary), or 3 o (Tertiary), by considering the number of carbons bound to the hydroxyl-bearing carbon. Ethanol is a primary alcohol because there is only one alkyl group attached to the carbon that carries the  OH substituent. The isopropyl alcohol found in rubbing alcohol is a secondary alcohol, An example of a tertiary alcohol is  tert -butyl (or  t -butyl) alcohol or 2-methyl-2-propanol. RCH 2 OH R 3 COH R 2 CHOH

4. R-O-H has a structure similar to that of water Higher boiling points. Hydrogen Bond in Water Hydrogen Bond in Alcohol

5. Classification of alcohols Solubility The Lower the molecular weight of alcohols, the higher the solubility in water. The water-solubility of alcohols depends on the length of the alkyl chain in the alcohol. alcohols having chains longer than four carbons are not very water-soluble. 3-4 carbons or less— ARE soluble in water Alcohols with more than one hydroxyl group ( polyhydroxyl alcohols) have higher boiling points than monohydroxyl alcohols. We already saw that the boiling points of alkanes increase with increasing chain length. The same is true for alcohols.

6. O CH3 H O CH3 H Alcohols having chains SHORTER than four carbons are very water-soluble… Methanol is Soluble and Miscible in water… Methanol

7. 2HC-2HC-2HC-3HC o H 2HC-2HC-2HC-3HC o H Butanol Alcohols having chains LONGER than Three carbons are not very water-soluble… Butanol is Soluble but not Miscible in water…

8. Formula Name Solubility in Water (g/100 g) CH 3 OH methanol infinitely soluble CH 3 CH 2 OH ethanol infinitely soluble CH 3 (CH 2 ) 2 OH propanol infinitely soluble CH 3 (CH 2 ) 3 OH butanol 9 CH 3 (CH 2 ) 4 OH pentanol 2.7 CH 3 (CH 2 ) 5 OH hexanol 0.6 CH 3 (CH 2 ) 6 OH heptanol 0.18 CH 3 (CH 2 ) 7 OH octanol 0.054 CH 3 (CH 2 ) 9 OH decanol insoluble in water Solubilities of ALCOHOL in water

9. Approximately 600,000 students per year are assaulted by a drinking student. Research suggests that women are more vulnerable than men to many alcohol- induced problems. Some of these include, Organ Damage, Trauma, Legal and interpersonal difficulties. Alcohol affects men and women differently. Women become more impaired than men from drinking the same amount of alcohol. This is because women: Are generally smaller in size Have less body water Have less dehydrogenase. Have more estrogen Alcohol is a central nervous system depressant. In small amounts it can have a relaxing effect.

10. Preparation of Alcohols 1.From alkenes ( i ) By acid catalysed hydration: Alcohols can be prepared by following methods (ii) By hydroboration–oxidation: 2. By reduction of carboxylic acids and esters: 3. By Fermentation Glucose + yeast ------  alcohol + carbon dioxide

11. Preparation of Alcohols By Fermentation How is alcohol made? Alcohol 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? Fermentation is the process in which yeast breaks down sugar into alcohol and carbon dioxide. Yeast are tiny single-celled fungi that contain special enzymes responsible for this reaction. The word equation for this process is : Glucose + yeast --------  alcohol + carbon dioxide 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.

12. Preparation of Alcohols By Fermentation   In this process {NADH}  donates its electrons to a derivative of pyruvate, producing ethanol. Going from pyruvate to ethanol is a two-step process. In the first step, a carboxyl group is removed from pyruvate and released in as carbon dioxide, producing a two-carbon molecule called acetaldehyde. In the second step , {NADH}  passes its electrons to acetaldehyde, regenerating  {NAD+} start forming ethanol.

13. Chemical reactions of alcohols Sure thing! Treating alcohols with HCl , HBr , or HI (which all fall under the catch-all term “HX” where X is a halide) results in the formation of alkyl halides. This occurs in a two step process: first, the alcohol is protonated to give its conjugate acid. Secondly, a substitution occurs. Halogenation of alcohol

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