CARBOXYLIC ACIDS Flashcards
WHATS THE GENERAL FORMULA FOR CARBOXYLIC ACIDS?
CnH COOH
2n+1
WHY ARE CARBOXYLIC ACIDS WITH FEWER THAN 6 CARBON ATOMS PER MOLECULE WATER SOLUBLE?
BECAUSE THEY CAN FORM HYDROGEN BONDS WITH THE FUNCTIONAL GROUP.
WHY ARE AQUEOUS SOLUTIONS ONLY SLIGHTLY IONISED?
TO GIVE LOW CONCENTRATIONS OF HYDRONIUM (H30+) AND ALKANOATE (CARBOXYLATE) IONS.
CARBOXYLIC ARE WEAK ACIDS. WHY?
BECAUSE THEY DONT COMPLETELY/ PARTIALLY DISSOCIATE IN WATER, TO GIVE h+
( HA <–> H++ A-) :
CARBOXYLIC ACIDS BEING WEAK ACIDS, MEANS THAT POSITION OF THE EQM LIES ________, AND THAT THE CONCETRATION OF __ IS MUCH SMALLER THAN THE CONC OF THE _____. HOW DOES THE CONCENTRATION OF H+ BEING SUFFICIENT ENOUGH, MAKE THIS USEFUL WHEN TESTING FOR THE POSSIBLE PRESENCE OF A CARBOXYLIC ACID?
CARBOXYLIC ACIDS BEING A WEAK ACID MEANS THAT THE EQUILIBRIUM LIES TO THE LEFT OF THE EQUATION, THIS MEANS THAT THE CONC OF H+ IONS MUCH SMALLER THAN THE CONC OF THE CARBOXYLIC ACID. HOWEVER THE CONC OF H+ IONS ARE SUFFICIENT ENOUGH TO REACT WITH AQEUOUS SODIUM CARBONATE (NA2CO3)/ (OR) SODIUM HYROGEN CARBONATE (NAHCO3), TO PRODUCE CO2, HENCE ALLOWING TO TEST FOR THE PRESENCE OF CARBOXYLIC ACID.
GIVE THE WORD AND IONIC EQUATION WITH CARBONATES, FOR SODIUM CARBONATE AND SODIUM HYDROGEN CARBONATE REACTING WITH CARBOXYLIC ACID?
sodium carbonate with carboxylic acid: 2RCOOH + na2co3 —–>2RCOO-NA+ + CO2 + H20
ionic equation with carbonates: 2RCOOH + CO3 2- —-> 2RCOO- +H20 + CO2
sodium hydrogen carbonate with carboxylic acid: RCOOH + NAHCO3 —–> RCOO-NA+ + CO2 + H20.
ionic equation with carbonates: RCOOH + C03- —-> RCOO- + CO2 + H20
ESTERS FORMED FROM WHAT IN WHAT TYPE OF REACTION. GIVE THE NAME OF THE WHOLE PROCESS OF MAKING ESTERS.
ESTERS ARE FORMED IN THE CONDENSATION REACTION BETWEEN AN ALCOHOL AND CARBOXYLIC ACID. THIS PROCESS IS ESTERIFICATION AND IS CONDENSATION AS ONE H20 IS LOST/RELEASED (or one small molecule not always h20, is released/lost eg acyl chloride with alcohol, hcl is lost/released).
esterfication is done in the presence of which acid(catalst/reagent)?
H2S04/HCL
ELABORATE ON THE USE OF AN ESTER IN FRAGRANCES + FLAVOURINGS, DUE TO ITS SWEEL AND FRUITY SMELL, AND EXPLAIN HOW THE SWEET AND FRUITY SMELL OF AN ESTER CAN BE USED AS A TEST FOR THE PRESENCE OF AN ALCOHOL OR CARBOXYLIC ACID.
FRAGRANCES + FLAVOURINGS:
ESTERS HAVE A FUITER AND SWEETER SMELL THAN ALDEHYDES/KETONES AND ARE RESPONSIBLE FOR THE MANY NATURAL FLOWER SCENTS AND FLAVOURS.
SYNTHETIC ESTERS CAN BE USED AS ARTIFICAL FUIT FLOWERS IN CONFECTIONARY PRODUCTS.
AROMAS AND TASTES ARE OFTEN CAUSED BY A COMPLEX MIX OF DIFF ESTERS.
HOW U CAN USE THIS FRUITY AND SWEET SMELL OF AN ESTER TO TEST FOR THE PRESENCE OF AN ALCOHOL OR CABOXYLIC ACID:
AN UNKOWN SUBSTANCE IS WARMED WITH CARBOXYLIC ACID IN THE PRESENCE OF CONCENTRATED SULFURIC ACID.
EXCESS ACID WITH ITS VINEGARY SMELL, CAN BE REMOVED BY ADDING WARM AQUEOUS SODIUM CARBONATE SOLUTION.
IF THE REMAINING MIXTURE HAS A SWEET SMELL OF AN ESTER, AN ALCOHOL IS PRESENT.
THE WARMTH OF THE SOLUTION CAUSES THE ESTER TO EVAPORATE HENCE THE SWEET SMELL IS EASILY DETECTED.
ESTERS CAN BE USED AS PLASTICISERS. PLASTICISERS ARE ADDITIVES WHICH CAN BE MIXED INTO POLYMERS TO INCREASE THE FLEXIBILITY OF THE POLYMER. PVC (POLY (CHLOROETHENE)), IS A RIGID POLYMER THAT CAN BE USED IN THE MAKING OF DRAIN PIPES AND GUTTERING. WHEN A SUITABLE ESTER PLASTICISER IS ADDED TO IT CAN BE MADE INTO CLING FILM, WHICH IS SOFT AND PLIABLE. EXPLAIN HOW ADDING A SUITABLE ESTER PLASTICISER TO PVC, INCREASES ITS FLEXIBILITY? (i.e. explain how an ester plasticiser works)
An ester plasticiser works by penetrating between the polymer chains, increasing the distance between them (hence reducing vdw’s).
this weakens the polar effects of the c-cl bond and and weakens the rigidity of the 3d strucutre if reduced, allowing the polymer chains to slide over one another.
what makes an ester like ethyl ethanoate to be used as a good solvent? and what can it be used in?
the fact that it has low toxicity, low volatility, as well as being relatively cheap, makes it an ideal solvent for use in glues, fragrances, and nail varnishes.
Triglycerides are naturally occuring what?
ESTERS
BIODIESEL IS PRODUCED IN WHICH PROCESS? and explain how its produced.( FROM WHAT)
TRANSESTERIFICATION. THE TRIGLYCERIDE IS CONVERTED/ TRANSESTERIFIED USING METHANOL (3 MOLES) INTO THE LESS VISCOUS FATTY ACID METHYL ESTER (FAME) AND GLYCEROL IS PRODUCED AS A BY-PRODUCT.
in the process of transesterification to produce biodiesel, an acid or an alkali can both be used to catalyse the reaction. explain how they work and which type of catalyst is more commonly used, giving 2 examples.
an acid works by protonating the carbonyl group, wheres an alkali works by diprotonating methanol. its more common to use an alkaline catalyst, like NaOH, KOH.
Transesterification is a reverisble reaction, hence what drives the eqm to the right.
excess of methanol is used to drive the eqm to the right
WHATS THE REVERSE OF ESTERIFICATION?
HYDROLYSIS (ALSO REVERSIBLE)
ESTER HYDROLYSIS IS A USEFUL REACTION FOR CREATING WHAT?
BIODEGRADEABLE PLASTICS.
ESTERS CAN BE HYDROLYSED BACK INTO ______ AND _______ OR SALTS OF _______, BY USING EITHER WHAT?
ESTERS CAN BE HYDROLYSED BACK INTO A CARBOXYLIC ACID AND AN ALCOHOL OR SALTS OF CARBOXYLIC ACID BY USING EITHER DILUTE ACID ( H2SO4), OR DILUTE ALKALI (NAOH) AND HEAT (UNDER REFLUX)
WHEN AN ESTER IS HEATED UNDER REFLUX WITH ACID, WHATS ESTABLISHED AND WHAT DOES THAT MEAN?
EQULIBRIUM IS ESTABLISHED, MEANING THAT THE HYDROLYSIS IS INCOMPLETE.
HEATING AN ESTER USING DILUTE ALKALI IS WHAT TYPE OF REACTION? AND HOW?
IRREVERSIBLE REACTION AS THE ESTER IS FULLY HYDROLYSED, SO THE REACTION GOES TO COMPLETION.
IN ALKALINE ESTER HYDROLYSIS, THE CARBOXYLIC ACID ONCE FORMED DOES WHAT?
REACTS WITH THE EXCESS DILUTE ALKALI (NAOH), TO FORM A CARBOXYLATE SALT AND ALCOHOL.
THE SODIUM CARBOXYLATE SALT FORMED IN ESTER ALKALI HYDROLYSIS, REQUIRES FURTHER ACIDIFICATION TO TURN INTO A CARBOXYLIC ACID, HENCE IT NEEDS TO GET WHAT? USING WHAT?
HENCE THE (COO-), NEEDS TO GET PROTONATED BY AN ACID LIKE HCL, TO FORM THE COOH, AND (NACL IS PRODUCED IN THE END AS A BYPRODUCT)
WHATS SAPONIFICATION?
WHEN VEGETABLE OILS AND ANIMALS FATS ( TRIGLYCERIDES) ARE HYDROLYSED IN ALKALINE CONDITIONS USING AQ NAOH, TO FORM SOAPS.
SOAPS ARE ____ SALTS OF WHAT?
CARBOXYLATE SALTS OF FATTY ACIDS.
