SOME EXAM QUESTIONS FOR CARBOXYLIC ACIDS Flashcards
HOW CAN THE VOLATILITY OF ESTERS BE EXPLOITED AS A TEST FOR THE PRESENCE OF ALCOHOLS. FOR EACH STEP STATE WHATS HAPPENING (6)?
S1) WARM THE UNKOWN SUBSTANCE WITH CARBOXYLIC ACID IN THE PRESENCE OF CONCENTRATED H2S04.
S2) ADD warm aqeuous NA2CO3.
S3) HEAT THE REACTION MIXTURE.
whats happening:
s1 - ester is being made
s2 - excess acidis being removed
s3 - ester is evaporating.
a plasticiser affects the structure of pvc. how? (3)
pushing the layers of polymer chains further apart hence reducing the strength of the IMF’s
hence the poylmer layers are able to slide over each other.
DEFINE BIODIESEL
A MIXTURE OF FATTY ACID METHYL ESTERS (FAME) MADE FROM RENEWABLE VEGETABLE OILS (TRIGLYERCIDES)
OCTYL ETHANOATE IS A FLAMMABLE ESTER. EXPLAIN WHY DISTILLATION WOULD NOT WORK TO SAFELY OBTAIN IT? and THEREFORE DESCRIBE THE EQUIPEMENT THE STEUDENT COULD USE TO OBTAIN THE ESTER SAFELY, AND EXPLAIN HOW THIS EQUIPMENT WOULD WORK.
THE ESTER IS FLAMMABLE, HENCE IT WOULD IGNITE USING A BUNSEN BURNER.
THE STUDENT SHOULD USE A SEPARATING FUNNEL, BECAUSE THE ESTER DOES NOT DISSOLVE IN WATER.
WHATS THE REAGENT AND CONDITIONS NEEDED FOR SAPONIFICATION?
HEAT UNDER REFLUX + AQ NAOH
ASPIRIN AND PARACETAMOL ARE RECRYSTALLISED TO PURIFY THE SOLIDS WHILE REMOVING ANY UNWANTED IMPURITIES. DESCRIBE THE PROCESS OF RECRYSTALLISATION? (5) (INCLUDE STEPS TO MINIMISE EARLY CRYSTALISATION OF SOLID)
DISSOLVE THE CRYSTALS IN MINIMUM VOLUME OF HOT SOLVENT.
FILTER THE HOT SOLUTION VIA A HOT FILTER.
LEAVE THE SOLUTION TO COOL AND RECRYSTALLISE
FILTER THE CRYSTALS UNDER REDUCED PRESSURE
WASH AND DRY
WHAT CHEMICAL IS RESPONSIBLE FOR WHITE FUMES?
HCL.
HOW CAN PROVE THE IDENTITY OF HCL?
TEST 1: ADD BLUE LITMUS PAPER, TURNS RED AND THEN BLEACHES.
TEST 2: ADD SILVER NITRATE SOLUTION, WHITE PPT FORMS
DEFINE VOLATILITY
ABILITY OF A SUBSTANCE TO EVAPORATE READILY AT NORMAL TEMPS
HIGHEST TO LOWEST VOLATILE OUT OF CARBOXYLIC ACIDS, ALCOHOL AND ESTER?
HIGHEST - CARBOXYLIC ACID
MIDDLE - ALCOHOL
LOWEST - ESTER.
CARBOXLYIC ACID IS A SHORTER HYDROCARBON CHAIN THAN ALCOHOLS, AS ITS HYDROCARBON CHAIN INTERFERES THE H-BONDING.
WHY DONT CARBOXYLIC ACIDS READILY UNDERGO NUCLEOPHILIC ADDITION-ELIMINATION REACTIONS WITH AMINES TO PRODUCE AN AMIDE?
THE AMINE REMOVES THE PROTON OF THE CARBOXYLIC ACID, FORMING A NEAGATIVELY CHARGED CARBOXYLATE ION WHICH IS HIGHLY STABLE, WHICH REPELS THE NUCLEPHILES.
STATE 3 FACTORS THAT AFFECT HOW READILY THE ACID DERIVATIVE (RCOZ), REACTS WITH A NUCLEOPHILE?
THE SIZE OF THE 𝛿+ CHARGE ON THE CARBONYL GROUP.
THE SIZE AND STRENGTH OF THE NUCLEOPHILE.
THE ELECTRON DONATING EFFECT OF THE Z GROUP.
DESCRIBE THE REACTION CONDITIONS REQUIRED TO PRODUCE BIODIESEL FROM THE TRIGLYCERIDE (2)
HEATING WITH 3 MOLES OF METHANOL
PRESENCE OF NAOH CATALYST.
WHY CAN SOMETHING LIKE GLYCEROL BE USED IN MEDICINAL CREAMS/ONITMENTS?
BECAUSE GLYCEROL HAS 3 HYROXYL GROUPS THAT CAN HYDROGEN BOND WITH WATER, REDUCING THE AMOUNT OF H20 LOST BY EVAPORATION (FROM THE CREAM)
