What Happens To Water Solubility As Chain Length Increases In Carboxylic Acids

CARBOXYLIC ACIDS

Their structure, chemistry and uses

See also 10b ESTERS � chemistry and uses (on a separate page)

Doc Brown's GCSE/IGCSE/O Level KS4 science�CHEMISTRY Revision Notes - Oil, useful products, environmental problems, introduction to organic chemistry

10a. Carboxylic Acids � structure, properties and uses

Carboxylic acids are a group of organic compounds which have weakly acidic properties.

Carboxylic acids react with metals, bases/alkalis to form salts

With metals, hydrogen is formed and they release carbon dioxide from carbonates.

They react with alcohols to form esters .

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Advanced Level notes on carboxylic acids & esters

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Revision notes on alkanes in chemistry, physical properties of carboxylic acids, uses of carboxylic acids, chemical reactions of carboxylic acids, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR 21st century science chemistry GCSE 9-1 chemistry examinations.

10a. CARBOXYLIC ACIDS We find members of the homologous series called carboxylic acids in fruits and in vinegar and many in fragrances and food additives as carboxylic acid derivatives called esters . Carboxylic acids The lower displayed formulae are a more accurate representation of the structure of the carboxylic acid molecules The full displayed formula for the first five members of the homologous series of CARBOXYLIC ACIDS These diagrams show ALL the covalent bonds (C-H, C-C, C-O, C=O and O-H) in carboxylic acids They can also be written in shorthand as: HCOOH,  CH3COOH,  CH3CH2COOH, CH3CH2CH2COOH and CH3CH2CH2CH2COOH The molecular structure of carboxylic acids Carboxylic acids form another homologous series and have the functional group �COOH. A homologous series is a family of compounds which have the same general formula and have a similar molecular structure and similar chemical properties because they have the same functional group of atoms (e.g. in this case the carboxylic acid -COOH group). The homologous series of carboxylic acids have the general formula CnH2n+1COOH where n = 0, 1, 2 etc. and equals the number of carbon atoms in the molecule minus 1. Note when n = 0 you simply get HCOOH methanoic acid. The functional group (COOH) is a group atoms common to all members of a homologous series that confer a particular set of characteristic chemical reactions on each member of the series e.g. in this series they all behave like acids with alkalis, carbonates etc., they all form compounds called esters when reacted with alcohols. Members of a  homologous series have similar physical properties such as appearance, melting/boiling points, solubility etc. BUT show trends in them e.g. steady increase in melting/boiling point with increase in carbon number or molecular mass. It is important to realise that members of a given homologous series like carboxylic acids have similar chemical reactions because their molecules contain the same functional group (COOH) and so you can predict the chemical reactions and products of the other members of the carboxylic series The structures of the first five members are shown above and the first  three members of the carboxylic acid homologous series are also shown given below. The last alcohol structure given below is the full displayed formula which you should definitely know, but you also need to know the various abbreviated ways of writing the molecular structure of alcohols. Carboxylic acid n ames end in ...oic acid (actually here they all end in ..anoic acid), and they start with meth, eth, prop etc. depending on the length of the carbon chain. and check out their formula from the general formula above, the final structure is the full displayed formula showing every covalent bond in the molecule (C�H, C=O, C�O, O�H, C�C) and note the arrangement of atoms in the COOH functional group, common to all the members of the homologous series of carboxylic acids. The first three are as follows ... methanoic acid (old name 'formic acid') ethanoic acid (old name 'acetic acid', in vinegar) propanoic acid (old name 'propionic acid') ADVANCED A Level revision notes on the structure and naming of CARBOXYLIC ACIDS and DERIVATIVES, including nomenclature of isomers (NOT needed for GCSE/IGCSE students!) The properties and uses of carboxylic acids This particular homologous series of carboxylic acids are colourless liquids with very strong odours (pungent smell) and tastes. The obnoxious smell of rancid butter and sweaty socks are due to the formation of carboxylic acids. It should be mentioned here that carboxylic acids with long carbon chains are called fatty acids, because they are combined with an alcohol called glycerol to form large ester molecules (glycerides/triesters) that make up most natural oils from plants and fat in animals. Many traditional soaps are made from natural oils and fats. The fatty acids may be saturated (no C=C double bonds) or unsaturated (with at least one C=C double bond) in the carbon chain. For more details on glycerides and soaps see Oils, fats, margarine and soaps Vinegar contains ethanoic acid (old name 'acetic acid') Ethanoic acid is used in the manufacture of the fibre, acetate rayon . Citrus fruits like oranges and lemons and many soft drinks contain the tri�carboxylic acid citric acid. and contribute to the 'tarter' or 'sour' taste of fruit. The molecule contains three acidic carboxylic acid groups �COOH (molecular structure on the right). Citric acid is a natural preservative (E330 on food labels) and is found in the largest quantities in oranges, lemons, limes and grapefruit. It is an anti�oxidant. Metal salts from citric acid, i.e. citrates, are used in dietary supplements to deliver trace metal minerals in a biologically available/absorbable chemical form. Citric acid can be used in baking powder to react with sodium bicarbonate giving the raising action from carbon dioxide gas formation. The same combination can be used to give the fizzy drink effect in medicines like ant�acid stomach powders. Citric acid is made in large quantities for the food industry, including fizzy drinks � which can be quite acid � dental concerns about the health of teeth here! Citric acid is strong enough to be used in some limescale removers � so think about your teeth when consuming all those fizzy drinks we might like! Aspirin is a carboxylic acid . Aspirin is a drug used for pain relief and is taken regularly by those at risk from heart attacks (see also Drugs). Ascorbic acid (vitamin C) is another carboxylic acid and is present in fresh fruit and vegetables and is vital for good health AND the body cannot synthesise it, so you must eat fruit and vegetables regularly! A lack of vitamin C can cause the disease scurvy. The symptoms of scurvy are skin sores, spongy gums and bleeding from mucous membranes. This is one example of malnutrition diseases caused by a vitamin deficiency in a diet. Long chain carboxylic acids, known as 'fatty acids', are used to make soaps and detergents , originally derived from plant oils. Carboxylic acids are weak acids The solubility of carboxylic acids in water decreases as the size of the molecule increases. They give all the normal reactions you expect of a carboxylic acid. Methanoic, ethanoic and propanoic acids are soluble in water, as are other carboxylic acids found in nature e.g. citric acid and ascorbic acid (Vitamin C) are both citrus in fruits. Typically weak acid solutions have a pH of around 2 to 6 (yellow�orange�pink with universal indicator), which is somewhat higher than strong acid solutions with a pH of 0 to 2. They are called weak acids because only a few % of the molecules in aqueous ionise to release protons (hydrogen ions, H+). It is the presence of hydrogen ions that makes aqueous solutions of carboxylic acids acid. e.g. for ethanoic acid (vinegar) around 98% remains unionised i.e. as the original neutral molecule and only ~2% form ethanoate ions and hydrogen ions.. CH3COOH(aq) CH3COO�(aq) + H+(aq) This is a reversible reaction with only 2% of the weak acid ionised on the right�hand side of the equilibrium. At similar concentrations, strong acids have a low pH of 0 or 1, because they are more fully ionised. Ethanoic acid will turn blue litmus pink and universal indicator gives an orangey�red colour. Being a weak acid, the pH is higher than in strong mineral acids like hydrochloric acid and the rate of reaction is slowed down too. For a more detailed discussion of these points see The theory of acids and bases Despite being a weak acid, carboxylic acids like ethanoic acid behave like any other acid and react with metals, alkalis and carbonate to form salts and fizzing here and there! Carboxylic acids react with metals and are neutralised by bases/alkalis This includes insoluble or soluble metal oxides, hydroxides and carbonates, to form salts . The salt names depends on the name of the acid, but the end of the name is ... oate. So aqueous solutions of methanoic acid form methanoate salts, ethanoic acid gives ethanoate salts, propanoic acid gives propanoate salts and butanoic acid gives butanoate salts on neutralisation. The salts can be crystallised from the solution by evaporation. Examples of salt formation: M etals react and dissolve to form a salts and hydrogen e.g. ethanoic acid + magnesium ==> magnesium ethanoate + hydrogen 2CH3COOH + Mg ====> (CH3COO)2Mg + H2 - butanoic acid + zinc ====> zinc butanoate + hydrogen 2CH3CH2CH2COOH + Zn ====> (CH3CH2CH2COO)2Zn + H2 - Not on the syllabus, but an interesting tragic story of 'old acetic acid' and lack of appreciation of chemical hazards. Ethanoic acid very slowly reacts with lead to form lead(II) ethanoate (old name lead acetate), once called 'sugar of lead' 2CH3COOH + Pb ====> (CH3COO)2Pb + H2 The salt formed was called 'sugar of lead' because it had a sweet taste! Cider makers in the past had dipped rods of lead into cider to neutralise any acetic acid that had formed and sweeten the beverage. Unfortunately, lead is one of many heavy metals and that are highly toxic and lead compounds affect the brain and nervous systems and can be fatal. Cases of lead poisoning have occurred through millennia, including the Romans, by using lead pots in food preparation or concentrating liquids. So, any cider left over that goes sour, dispose of it or let turn completely into cider vinegar for the kitchen! - Alkalis (soluble bases) react to form a carboxylic acid salt and water  e.g. ethanoic acid + sodium hydroxide ===> sodium ethanoate + water CH3COOH + NaOH ====> CH3COONa + H2O - ethanoic acid + potassium hydroxide ===> potassium ethanoate + water CH3COOH + KOH ====> CH3COOK + H2O - propanoic acid + sodium hydroxide ===> sodium propanoate + water CH3CH2COOH + NaOH ====> CH3CH2COONa + H2O - I nsoluble bases dissolve and react to form salt and water e.g. zinc oxide + ethanoic acid ====> zinc ethanoate + water 2CH3COOH + ZnO ====> (CH3COO)2Zn + H2O - ethanoic acid + calcium hydroxide ====> calcium ethanoate + water 2CH3COOH + Ca(OH)2 ====> (CH3COO)2Ca + 2H2O - ethanoic acid + magnesium hydroxide ====> magnesium ethanoate + water 2CH3COOH + Mg(OH)2 ====> (CH3COO)2Mg + 2H2O - butanoic acid + magnesium hydroxide ====> magnesium butanoate + water 2CH3CH2CH2COOH + Mg(OH)2 ====> (CH3CH2CH2COO)2Mg + 2H2O - C arbonate and hydrogencarbonate bases produce a carboxylic acid salt, water and carbon dioxide gas e.g. ethanoic acid + sodium hydrogen carbonate ==> sodium ethanoate + water + carbon dioxide CH3COOH + NaHCO3 ====> CH3COONa + H2O + CO2 - ethanoic acid + sodium carbonate ====> sodium ethanoate + water + carbon dioxide 2CH3COOH + Na2CO3 ====> 2CH3COONa + H2O + CO2 - propanoic acid + sodium carbonate ====> sodium propanoate + water + carbon dioxide 2CH3CH2COOH + Na2CO3 ====> 2CH3CH2COONa + H2O + CO2 � ethanoic acid + magnesium carbonate ==> magnesium ethanoate + water + carbon dioxide 2CH3COOH + MgCO3 ====> (CH3COO)2Mg + H2O + CO2 � ethanoic acid + calcium carbonate ==> calcium ethanoate + water + carbon dioxide 2CH3COOH + CaCO3 ====> (CH3COO)2Ca + H2O + CO2 - Aqueous ammonia solution forms ammonium salts e.g. methanoic acid + ammonia ====> ammonium methanoate HCOOH + NH3 ====> HCOONH4 - ethanoic acid + ammonia ==> ammonium ethanoate CH3COOH + NH3 ====> CH3COONH4 - Strictly speaking, ammonium hydroxide doesn't really exist, but in older texts you will find these reactions written in this way, but NOT correct e.g. propanoic acid + ammonium hydroxide ==> ammonium propanoate + water CH3CH2COOH + NH4OH ==> CH3CH2COONH4 + H2O - ESTERS: AMINO ACIDS Advanced Level notes on carboxylic acids & esters

Revision notes on alkanes in chemistry, physical properties of carboxylic acids, uses of carboxylic acids, chemical reactions of carboxylic acids, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR 21st century science chemistry GCSE 9-1 chemistry examinations. TOP OF PAGE GCSE/IGCSE/O Level Oil Products & Organic Chemistry INDEX PAGE See also Esters, chemistry and uses including perfumes ALL my Advanced A Level Organic Chemistry revision notes Advanced Level notes on carboxylic acids & esters Multiple Choice Quizzes and Worksheets KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (easier�foundation�level) KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (harder�higher�level) KS4 Science GCSE/IGCSE m/c QUIZ on other aspects of Organic Chemistry and 3 linked easy Oil Products gap�fill quiz worksheets ALSO gap�fill ('word�fill') exercises originally written for ... ... Ex AQA GCSE Science Useful products from crude oil AND Oil, Hydrocarbons & Cracking etc. ... Ex OCR 21st C GCSE Science Worksheet gap�fill C1.1c Air pollutants etc ... ... Ex Edexcel GCSE Science Crude Oil and its Fractional distillation etc ... ... each set are interlinked, so clicking on one of the above leads to a sequence of several quizzes ALL my Advanced A Level Organic Chemistry revision notes Advanced Level notes on carboxylic acids & esters keywords equations: CH3CH2OH + O2 ==> CH3COOH + H2O Revision notes on alkanes in chemistry, physical properties of carboxylic acids, uses of carboxylic acids, chemical reactions of carboxylic acids, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR 21st century science chemistry GCSE 9-1 chemistry examinations. These revision notes on the uses and chemical properties of carboxylic acids should prove useful for the NEW AQA GCSE chemistry, Edexcel GCSE chemistry & OCR GCSE chemistry (Gateway & 21st Century) GCSE (9�1), (9-5) & (5-1) science courses. Revision notes on carboxylic acids reactions uses KS4 Science GCSE/IGCSE/O level Chemistry Information on carboxylic acids reactions uses for revising for AQA GCSE Science, Edexcel Science chemistry IGCSE Chemistry notes on carboxylic acids reactions uses OCR 21st Century Science, OCR Gateway Science notes on carboxylic acids reactions uses WJEC gcse science chemistry notes on carboxylic acids reactions uses CIE O Level chemistry CIE IGCSE chemistry notes on carboxylic acids reactions uses CCEA/CEA gcse science chemistry (help for courses equal to US grade 8, grade 9 grade 10) science chemistry courses revision guides explanation chemical equations for carboxylic acids reactions uses educational videos on carboxylic acids reactions uses guidebooks for revising carboxylic acids reactions uses textbooks on carboxylic acids reactions uses gcse chemistry revision free detailed notes on structure & chemistry of carboxylic acids to help revise igcse chemistry igcse chemistry revision notes on structure & chemistry of carboxylic acids O level chemistry revision free detailed notes on structure & chemistry of carboxylic acids to help revise gcse chemistry free detailed notes on structure & chemistry of carboxylic acids to help revise O level chemistry free online website to help revise structure & chemistry of carboxylic acids for gcse chemistry  free online website to help revise structure & chemistry of carboxylic acids for igcse chemistry free online website to help revise O level structure & chemistry of carboxylic acids chemistry how to succeed in questions on structure & chemistry of carboxylic acids for gcse chemistry how to succeed at igcse chemistry how to succeed at O level chemistry a good website for free questions on structure & chemistry of carboxylic acids to help to pass gcse chemistry questions on structure & chemistry of carboxylic acids a good website for free help to pass igcse chemistry with revision notes on structure & chemistry of carboxylic acids a good website for free help to pass O level chemistry CH3COOH(aq) CH3COO�(aq) + H+(aq) CH3CH2COOH(aq) CH3CH2COO�(aq) + H+(aq) CH3CH2CH2COOH(aq) CH3CH2CH2COO�(aq) + H+(aq) 2CH3COOH + Mg ====> (CH3COO)2Mg + H2 2CH3CH2CH2COOH + Zn ====> (CH3CH2CH2COO)2Zn + H2 CH3COOH + NaOH ====> CH3COONa + H2O CH3COOH + KOH ====> CH3COOK + H2O CH3CH2COOH + NaOH ====> CH3CH2COONa + H2O 2CH3COOH + ZnO ====> (CH3COO)2Zn + H2O 2CH3COOH + Ca(OH)2 ====> (CH3COO)2Ca + 2H2O 2CH3COOH + Mg(OH)2 ====> (CH3COO)2Mg + 2H2O 2CH3CH2CH2COOH + Mg(OH)2 ====> (CH3CH2CH2COO)2Mg + 2H2O CH3COOH + NaHCO3 ====> CH3COONa + H2O + CO2 2CH3COOH + Na2CO3 ====> 2CH3COONa + H2O + CO2 2CH3CH2COOH + Na2CO3 ====> 2CH3CH2COONa + H2O + CO2 CH3COOH + MgCO3  ====> (CH3COO)2Mg + H2O + CO2 2CH3COOH + CaCO3  ====> (CH3COO)2Ca + H2O + CO2 CH3COOH + NH3 ====> CH3COONH4 Advanced Level notes on carboxylic acids & esters TOP OF PAGE

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GCSE/IGCSE/O Level Oil Products & Organic Chemistry INDEX PAGE

See also Esters, chemistry and uses including perfumes

ALL my Advanced A Level Organic Chemistry revision notes

A Level notes on carboxylic acids & esters

What Happens To Water Solubility As Chain Length Increases In Carboxylic Acids

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