Organics 2 Flashcards
(40 cards)
1
Q
Esters
A
-carboxylic acid derivative
- ester group, COO
- oate ending
2
Q
Esterification
A
condensation reaction between carboxylic acid and alcohol, with conc H2SO4 as a catalyst
- reversible reaction
- slow + needs heat under reflux
-low yields
3
Q
Esterification other method
A
reacting acid anhydrides (another carboxylic acid derivative) and alcohols at room temperature.
4
Q
Hydrolysis of Esters
A
- reforms carboxylic acid by using either dilute acid or dilute alkali
- when heated under reflux with dilute acid, equilibrium mixture forms so reaction is reversible
- reaction is irreversible with dilute alkali as the ester is fully hydrolysed
- carboxylate salt is first produced, needs further acidification to form carboxylic acid
5
Q
Acyl chlorides
A
- contain -COCL functional group
- prepared from reaction of carboxylic acids with Liquid Sulfur dichloride oxide (SOCL2)
- reaction makes acyl chloride + SO2 + HCL
- increased reactivity of acyl chlorides compared to carboxylic acids
6
Q
Formation of Esters from Acyl Chlorides
A
- react with alcohols and phenols( requires heat and a base) to form esters
- faster reaction than cooh
- ADD/ELIM reaction
- alcohol or phenol ADD across C=O bond
- HCL mol is ELIM
6
Q
Uses of Acyl Chlorides
A
- addition-elimination reactions: addition of a small molecule across the C=O bond takes place, followed by the elimination of a small molecule
- Hydrolysis
- Reaction w alcohols and phenols to form esters
- Reaction w ammonia and amines to form amides
6
Q
Hydrolysis of Acyl Chlorides
A
- formation of a carboxylic acid and HCL molecule
- ADD/ELIM reaction
- H2O adds across C=O, HCL molecule is ELIM
7
Q
Formation of Amides from Acyl Chlorides
A
- form from condensation reactions with amines and ammonia
- N atom has a lone pair of E- that can attack the carbonyl C atom in acyl chlorides
- Primary amide (when reacted w ammonia)
-Secondary amide (when reacted with primary amines)
-ADD/ELIM - amine/ ammonia mol ADD across C=O bond
- HCL mol is ELIM
8
Q
Amines
A
- no of substituted H is basis for classifying amines
-amine prefix - N atom in ammonia or amine can accept a proton (H+ ion)
- Therefore act as bases in aqueous solutions as they donate its lone pair of electrons to form a dative bond
9
Q
Preparing Amines
A
- reaction of halogenoalkanes with ammonia
- Reduction of nitriles
10
Q
Reaction of halogenoalkanes with ammonia
A
- Nuc Sub reaction
- Lone pair on N acts as a nucleophile and replaces the halogen ( with NH2)
- excess, hot ethanolic ammonia under pressure, primary amine is formed
11
Q
Reduction of nitriles
A
- nitriles contain a -CN functional group which can be reduced to a -NH2 group
- nitrile vapour and H2 Gas are passed over a Ni catalyst or LiAlH4 in dry ether to form primary amine
12
Q
Reaction of halogenoalkanes with primary amine
A
- NUC SUB, N in primary amine acts as nucleophile and replaces halogen
- halogenoalkane + primary amine in ethanol and heated under pressure, secondary amine is formed
13
Q
Preparing Aromatic Amines
A
- Nitrobenzene (C6H5NO2) can be reduced to phenylamine (C6H5NH2)
14
Q
Stage 1- Reduction of Nitrobenzene
A
- react nitrobenzene with Tin, Sn and conc HCL (Sn and HCL act as reducing agents)
- heat under reflux
- phenulammonium ions, C6H5NH3+ are protonated due to acidic conditions
15
Q
Stage 2- Formation of phenylamine
A
- phenylammonium ions, C6H5NH3+ are deprotonated by the addition of excess sodium hydroxide solution, NaOH (aq)
16
Q
Amino acids
A
- organic compounds
- 2 functional groups: basic amino (-NH2) group and an acidic carboxylic acid (-COOH) group
- amphoteric, can act as acid + base
17
Q
Naturally occurring amino acids
A
- 20 naturally occurring amino acids with general formula RCH(NH2)COOH
- R group varies in different amino acids, can be acidic, basic or neutral
18
Q
Reactions of the amine group in amino acids
A
- amine group is basic, reacts with acids to make salts
19
Q
Reactions with the carboxylic acid group in amino acids
A
- amino acid reacts with aqueous alkali, such as sodium or potassium hydroxide, to form a salt and water
20
Q
Esterification with alcohols- AA
A
- can be esterified by heating with alcohol in the presences of conc sulfuric acid
- carboxylic acid group is esterified whilst the basic amine group is protonated due to the acidic conditions
21
Q
Amides
A
- formed from condensation reaction of carboxylic acids or acyl chlorides with ammonia or amines
- general structure RCONR2
- add -amide to end for primary amides
- for secondary amides, alkyl chain attached to the N is added at the start. alkyl chain is prefixed N- then -amide
22
Q
stereoisomers
A
- molecules that have the same structural formula but have atoms arranged differently in space
- 2 types, Geometrical (E/Z) and Optical
23
Chiral centre
- a carbon atom that has four different atoms of groups of atoms attached to its centre
- compounds with a chiral centre exist as 2 optical isomers (also known as enantiomers)
24
Enantiomers
- non-superimposable mirror images of each other
25
Condensation polymers
- polymer is produced by repeated condensation reactions between monomers
- can be identified because the monomers are linked by ester or amide bonds
can be formed by:
-dicarboxylic acids and diols
-dicarboxylic acids and diamines
- amino acids
26
Polyester
- formed by the reaction between dicarboxylic acid monomers and diol monomers
- Polyester is produced by linking these monomers with ester bonds/links
27
Formation of polyesters
diol (2 OH groups) + carboxylic acid (2 COOH groups)
- when polyester forms, one of the -OH groups on diol and H atom of -COOH are expelled as H2O mol
- results in polyester
28
Formation of polyesters - hydroxycarboxylic acids
hydroxycarboxylic acids contain: alcohol group at one end and carboxylic acid group at other end
- they join to each other to make polyester
29
Polyamides
- polymers where repeated units are bonded together by amide links
- formula of an amide group is -C=ONH
30
Polyamide monomers
- diamine (2 -NH2 groups) and dicarboxylic acid ( 2 COOH ) are required to form polyamide
- dioyl dichlorides ( 2 -COCl) can also be used to react with diamine instead of the acid; more reactive but more expensive
31
Amino acids- formation of proteins
- dipeptides can be produced by polymerising 2 amino acids together: amine group (-NH2) and acid group (-COOH) of each amino acid is used to polymerise with another amino acid
- polypeptides are made through polymerising more than 2 amino acids together
32
Biodegradable polymers
- both polyesters and polyamides can be broken down using hydrolysis reactions
- major advantage over the polymers produced using alkene monomers (polyalkenes)
- they can be broken down easily and their products used for other applications
33
Hydrolysis of polyamides
- in acidic hydrolysis, an acid such as HCL acts as the catalyst: polyamides such as Kevlar are heated with dilute acid, breaking the polyamide into a dicarboxylic acid and ammonium ions
- In alkaline hydrolysis, the polyamide is heated with a species containing hydroxide ions (eg NaOH), breaking the polymer into the sodium salts of its monomers (dicarboxylic acid salt and diamines)
34
Hydrolysis of polyesters
- acid hydrolysis (H+/H2O) form the diol and carboxylic acid
- alkaline hydrolysis (NaOH/H2O) forms the diol and carboxylic acid salt
35
Formation of Nitriles
- nucleophile in this reaction is the cyanide, CN- ion
- Ethanolic solution of potassium cyanide (KCN in ethanol) is heated under reflux with the halogenoalkane
- The product is a nitrile
- The nuc sub of halogenoalkanes with KCN adds an extra C atom to the C chain
36
Addition of HCN to carbonyl compounds
- NUC/ADD of HCN to carbonyl compounds is a 2 step process
Step 1: cyanide ion attacks carbonyl carbon to form a negatively charged intermediate
Step 2 : negatively charged oxygen atom in the reactive intermediate quickly reacts with aqueous H+ (either from HCN, water or dilute acid) to form 2- hydroxynitrile compounds
37
Hydrolysis of Nitriles
- nitriles are hydrolysed by either dilute acid or dilute alkali followed by acidification
hydrolysis by dilute acid: forms carboxylic acid and ammonium salt
hydrolysis by dilute alkali: forms sodium carboxylate salt and ammonia: acidification is required to change carboxylate ion into a carboxylic acid
CN group converted to -COOH group
38
Reduction of Nitriles
-
