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Chemistry A-level OCR A > Organics 2 > Flashcards

Organics 2 Flashcards

1
Q

Esters

A

-carboxylic acid derivative
- ester group, COO
- oate ending

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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

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3
Q

Esterification other method

A

reacting acid anhydrides (another carboxylic acid derivative) and alcohols at room temperature.

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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
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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
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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
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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
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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
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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
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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
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9
Q

Preparing Amines

A
  • reaction of halogenoalkanes with ammonia
  • Reduction of nitriles
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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
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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
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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
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13
Q

Preparing Aromatic Amines

A
  • Nitrobenzene (C6H5NO2) can be reduced to phenylamine (C6H5NH2)
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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
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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
Q

Chiral centre

A
  • 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
Q

Enantiomers

A
  • non-superimposable mirror images of each other
25
Q

Condensation polymers

A
  • 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
Q

Polyester

A
  • formed by the reaction between dicarboxylic acid monomers and diol monomers
  • Polyester is produced by linking these monomers with ester bonds/links
27
Q

Formation of polyesters

A

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
Q

Formation of polyesters - hydroxycarboxylic acids

A

hydroxycarboxylic acids contain: alcohol group at one end and carboxylic acid group at other end
- they join to each other to make polyester

29
Q

Polyamides

A
  • polymers where repeated units are bonded together by amide links
  • formula of an amide group is -C=ONH
30
Q

Polyamide monomers

A
  • 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
Q

Amino acids- formation of proteins

A
  • 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
Q

Biodegradable polymers

A
  • 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
Q

Hydrolysis of polyamides

A
  • 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
Q

Hydrolysis of polyesters

A
  • acid hydrolysis (H+/H2O) form the diol and carboxylic acid
  • alkaline hydrolysis (NaOH/H2O) forms the diol and carboxylic acid salt
35
Q

Formation of Nitriles

A
  • 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
Q

Addition of HCN to carbonyl compounds

A
  • 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
Q

Hydrolysis of Nitriles

A
  • 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
Q

Reduction of Nitriles

A

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Chemistry A-level OCR A (2 decks)

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