Download presentation
Presentation is loading. Please wait.
1
Alcohols – nomenclature and reactions
L.O. To be able to name alcohols and assign primary, secondary and tertiary status. To know some specific reactions of alcohols C OH H C OH C H OH
2
OH at junction of 2 chains
TYPES OF ALCOHOL PRIMARY ALCOHOLS SECONDARY ALCOHOLS TERTIARY ALCOHOLS C H OH C OH H C OH OH at end of a chain OH at middle of a chain OH at junction of 2 chains CH3CH2CH2CH2OH CH3CH2CH(OH)CH3 CH3C(CH3)(OH)CH3 Butan-1-ol Butan-2-ol Methyl propan-2-ol
3
SELECT PRIMARY (P), SECONDARY (S) OR TERTIARY (T)
ISOMERS OF PENTANOL Make sure you can draw full displayed, structural and skeletal representations of each. SELECT PRIMARY (P), SECONDARY (S) OR TERTIARY (T) CH3CH2CH2CH2CH2OH Pentan-1-ol CH3CH2CH2CH(OH)CH Pentan-2-ol CH3CH2C(CH3)(OH)CH Methylbutan-2-ol CH3CH2CH(OH)CH2CH Pentan-3-ol CH3C(CH3)2CH2OH ,2-Dimethylpropan-1-ol CH3CH(OH)CH(CH3)CH Methylbutan-2-ol CH3CH(CH3)CH2CH2OH 3-Methylbutan-1-ol CH3CH2CH(CH3)CH2OH Methylbutan-1-ol P S T P S T P S T P S T P S T P S T P S T P S T
4
Dehydration (removal of water) of alcohols ALKENES
Removal (elimination) of water by : 1.Heating with concentrated sulphuric acid at 170C or 2. Passing vapour over Al2O3 at 350C C Used to make ETHENE in countries where carbohydrate plentiful for fermentation but petroleum oil not avialable for cracking + HOH NB H may be removed from more than one C adjacent to C-OH mixture of alkenes
5
1. 2. 3. C OH H H C OH CH3 C OH H C H C CH3 H C CH2CH3 H + HOH C H CH3
Deduce the dehydration products of : 1. Ethanol? 2. Methyl-propan-2-ol? 3. Butan-2-ol ? 1. 2. 3. C OH H H C OH CH3 C OH H C H C CH3 H C CH2CH3 H + HOH C H CH3 + HOH + HOH E & Z! and
6
C-OH + Na C-O- Na+ + ½ H2 HOH + Na Na+OH- + ½ H2
Reaction of an alcohol (R-OH) with sodium metal an alkoxide (R-O- Na+) + hydrogen gas (H2) C-OH + Na C-O- Na+ + ½ H2 Notes : 1. The bonding is ionic between O and Na 2. The reaction is parallel (but slower) to the reaction of sodium with the OH group in water HOH + Na Na+OH- + ½ H2 Note : These are all redox reactions because the Na is oxidised (electron loss) and the H of OH is reduced (electron gain)
7
For isomeric alcohols:
PRIMARY ALCOHOLS SECONDARY ALCOHOLS TERTIARY ALCOHOLS C H OH C OH H C OH Rate decrease For isomeric alcohols: the rate of reaction with sodium decreases from primary to secondary to tertiary
8
1. 2. 3. C OH H H C OH CH3 C OH H + Na + Na + Na C O- Na+ H H C O- Na+
Products of sodium with : 1. Ethanol? 2. Methyl-propan-2-ol? 3. Butan-2-ol ? 1. 2. 3. C OH H H C OH CH3 C OH H + Na + Na + Na C O- Na+ H H C O- Na+ CH3 C O-Na+ H Sodium ethoxide Sodium (methylprop-2-oxide) Sodium but-2-oxide + ½H2 + ½H2 + ½H2
9
Try some more examples for yourself!
Write an equation, giving the full structure and name of the main organic product, for the reactions between : 1. Methanol + Na 2. Propan-1-ol + Na 3. Propan-2-ol + Na 4. Butan-1-ol + Na 5. Methyl-propan-1-ol + Na
10
C-OH + HBr C-Br + H2O Substitution of an alcohol by HBr
a bromoalkane δ+ δ- C-OH + HBr C-Br + H2O HBr produced by reacting KBr with conc. H2SO4. KBr + H2SO4 KHSO4 + HBr In practice, the alcohol is mixed with KBr in a reflux apparatus. The acid is then added to the mixture, drop wise. Note : This is a nucleophilic substitution because the δ+C is attacked by the δ-Br
11
1. 2. 3. C OH H H C OH CH3 C OH H + HBr + HBr + HBr C Br H H C Br CH3
HBr substitution products of :1. Ethanol? 2. Methyl-propan-2-ol? 3. Butan-2-ol ? 1. 2. 3. C OH H H C OH CH3 C OH H + HBr + HBr + HBr C Br H H C Br CH3 C Br H Bromoethane Methyl-2-bromopropane 2-Bromobutane + H2O + H2O + H2O
12
C-Cl (l) +HCl (g) + POCl3 (l) R-OH (l) + PCl5 (s)
Reaction of alcohols with phosphorus pentachloride (PCl5) R-OH (l) + PCl5 (s) C-Cl (l) +HCl (g) + POCl3 (l) Fumes of HCl being given off makes this a useful reaction to identify the presence of an alcohol functional group.
13
Try some more examples for yourself!
Give the full structure and name of the main organic product produced by : 1. Methanol + HBr 2. Propan-1-ol + HBr 3. Propan-2-ol + HCl 4. Butan-1-ol + HBr 5. Methyl-propan-1-ol + HCl
14
AS Chemistry OXIDATION OF ALCOHOLS
15
OXIDATION OF ALCOHOLS Oxidised to aldehydes and acids or ketones
NOT SIGNIFICANT for TERTIARY alcohols! for PRIMARY alcohols for SECONDARY alcohols -CH2OH -C-CH(OH)-C- NB Oxidant = hot acidified Cr2O72- [dichromate(VI)] ion] Provided by mixture of potassium dichromate(VI), K2Cr2O7, and excess dilute sulphuric acid, H2SO4. Oxidant is represented by : [O] OBSERVATION: Orange Cr2O72- reduced to green Cr3+
16
C H OH C H OH C OH + [O] + [O] + [O] C O H C O + H2O + H2O
SECONDARY PRIMARY TERTIARY C H OH C H OH C OH + [O] + [O] + [O] C O H C O NO SIGNIFICANT OXIDATION + H2O + H2O - no C–H bond Aldehyde Ketone Any oxidation that does occur involves breaking C-C bonds loss of original structure. + [O] + [O] C O OH NO FURTHER OXIDATION Acid - no C – H bond
17
What are the oxidation products of :
1. Ethanol? 2. Methyl-propan-2-ol? 3.Butan-2-ol? CH3CH2OH CH3C(CH3)(OH)CH3 CH3CH2CH(OH)CH3 Primary Tertiary Secondary
18
Controlling Oxidation Products
To Maximise the Production of an ALDEHYDE To Maximise the Production of an ACID or a KETONE This is PARTIAL oxidation This is FURTHER oxidation Use only molar proportions of dichromate and acid Use excess of dichromate and acid Use minimum contact time between alcohol and oxidant by use of immediate distillation Use maximum contact time between alcohol and oxidant by use of reflux Add acidified dichromate to the alcohol to avoid the presence of excess oxidant Pre-mix acidified dichromate and alcohol to ensure excess oxidant at all times
19
1 2 3 4 5 Halogeno- alkane C-Br Alcohol C-OH Primary amine C-NH2
Alkene(s) C=C Ketone C-CO-C (if alcohol SECONDARY) Aldehyde CHO PRIMARY) Acid COOH Ester CO.OC 1. Reflux with conc. NaOH in ethanol 3. Heat with excess conc. NH3 in ethanol 2. + HBr 3. Reflux with aq. NaOH 3. Heat with NaBr + conc. H2SO4 1 2 3 4 5 1. Heat with conc. H2SO4 Eliminations Electrophilic addition 5. Heat with carboxylic acid (-COOH) + conc. H2SO4 cat. Nucleophilic substitutions Oxidations 4. Reflux with excess K2Cr2O7 + dil. H2SO4 5. Heat with alcohol (C-OH) + conc. H2SO4 catalyst Condensations 4. Heat with molar propns. of K2Cr2O7 + dil. H2SO4 ; distil 4. Reflux with excess K2Cr2O7 + dil. H2SO4
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.