Carboxylic Acids 2/3/20 Carboxylic Acids Lesson objective: To

Carboxylic Acids 2/3/20 Carboxylic Acids Lesson objective: To

Carboxylic Acids 2/3/20 Carboxylic Acids Lesson objective: To know about carboxylic acids Success criteria: Identify the carboxylic acid functional group Explain the physical properties of carboxylic acids, in relation to their boiling temperatures and solubility

Explain how carboxylic acids can be prepared Explain the reactions of carboxylic acids with: - lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether -bases to produce salts Carboxylic acids Carboxylic acids have a carboxyl group (-COOH) consisting of a carbonyl group and a hydroxyl group attached to the

terminal carbonyl carbon. Carboxylic acids are named using the suffix oic acid. Methanoic acid is the simplest carboxylic acid and is found in bee and ant stings. Ethanoic acid is the acid that gives vinegar its sharp taste and smell. It is also important in the chemical industry and about 6.5 million tonnes are used worldwide each year

Naming Carboxylic Acids Methanoic acid, HCOOH Ethanoic acid, CH3COOH Propanoic acid, CH3CH2COOH Carboxylic Acids Carboxylic acids contain -COOH methanoic acid (HCOOH)

6 of 30 ethanoic acid (CH3COOH) propanoic acid (CH3CH2COOH) Boardworks Ltd 2009 Naming carboxylic acids

Carboxylic Acids Lesson objective: To know about carboxylic acids Success criteria: Identify the carboxylic acid functional group Explain the physical properties of carboxylic acids, in relation to their boiling temperatures and solubility Explain how carboxylic acids can be prepared Explain the reactions of carboxylic acids with:

- lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether -bases to produce salts Making Carboxylic Acids You can oxidise primary alcohols and aldehydes If you oxidise a primary alcohol you will first oxidise it to an aldehyde, this will then be further oxidised to a carboxylic acid Often acidified potassium dichromate is used (K2Cr2O7/H2SO4)

E.g. CH3CH2CH2OH + 2[O] CH3CH2COOH + H2O Propan 1 ol CH3CH2CHO + [O] CH3CH2COOH Propanal Making Carboxylic Acids You make them by hydrolysing a nitrile You reflux the nitrile with dilute hydrochloric acid You then distil off the carboxylic acid E.g.

CH3CH2CN + H+ + 2H2O CH3CH2COOH + NH4+ Carboxylic Acids Lesson objective: To know about carboxylic acids Success criteria: Identify the carboxylic acid functional group Explain the physical properties of carboxylic acids, in relation to their boiling temperatures and solubility

Explain how carboxylic acids can be prepared Explain the reactions of carboxylic acids with: - lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether -bases to produce salts Physical Properties What intermolecular forces are there between carboxylic acid molecules? +

- + Physical Properties The intermolecular forces between carboxylic acids include: London forces Permanent dipole dipole forces (due to their polar C = O, C O and O H bonds Hydrogen bonds (unlike carbonyl

compounds) How do you think these affect their physical properties? Physical Properties Carboxylic acids with fewer than about 10 carbon atoms are liquids at room temperature. Their boiling temperatures increase as their molar masses increase and the London forces increase.

Physical Properties In pure, liquid carboxylic acids, dimers can also form. This is when a molecule hydrogen bonds with just one other molecule. This increases the size of the molecule, increasing the intermolecular forces and so their boiling point.

Solubility in water Very small carboxylic acids are soluble in water. The highly polar C = O and O H bonds

allow carboxylic acid molecules to form hydrogen bonds with water molecules. As the number of carbon atoms in the carbon acids increases, the solubility decreases. This is the result of the longer non polar hydrocarbon chain in the molecule, which does not interact with water molecules. Solubility of carboxylic acids Carboxylic acids

with between one and four carbon atoms are very soluble in water. The highly polar C = O and O H bonds allow carboxylic acid molecules to form hydrogen bonds with water molecules.

Solubility of carboxylic acids Carboxylic Acids Lesson objective: To know about carboxylic acids Success criteria: Identify the carboxylic acid functional group Explain the physical properties of carboxylic acids, in relation to their boiling temperatures and solubility Explain how carboxylic acids can be prepared

Explain the reactions of carboxylic acids with: - lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether -bases to produce salts Reacting with bases Carboxylic acids are neutralised by aqueous bases (alkalis) to form salts and water CH3COOH + NaOH CH3COONa + H2O Ethanoic acid Sodium ethanoate With carbonates and hydrogencarbonates

carbon dioxide is also made Salts of carboxylix acids are called carboxylates. Their names end in -oate Reacting with bases Carboxylic acids are neutralised by aqueous bases (alkalis) to form salts and water They are weak acids CH3COOH + NaOH CH3COONa + H2O Ethanoic acid Sodium ethanoate

With carbonates and hydrogencarbonates carbon dioxide is also made Salts of carboxylix acids are called carboxylates. Their names end in -oate Reaction with lithium tetrahydridoaluminate It is hard to reduce a carboxylic acid, you need a powerful reducing agent. E.g. LiAlH4 in dry ether (lithium tetrahydridoaluminate, lithium aluminium

hydride) It reduces the carboxylic acid right down to an alcohol. You cant get the reduction to stop at the aldehyde. E.g. CH3CH2COOH + 4[H] CH3CH2CH2OH + H2O Propan-1-ol Reaction with lithium tetrahydridoaluminate It is hard to reduce a carboxylic acid, you need a

powerful reducing agent. E.g. LiAlH4 in dry ether (lithium tetrahydridoaluminate, lithium aluminium hydride) It reduces the carboxylic acid right down to an alcohol. You cant get the reduction to stop at the aldehyde. E.g. CH3CH2COOH + 4[H] CH3CH2CH2OH + H2O Propanoic acid

Propan-1-ol Reaction with lithium tetrahydridoaluminate It is hard to reduce a carboxylic acid, you need a powerful reducing agent. E.g. LiAlH4 in dry ether (lithium tetrahydridoaluminate, lithium aluminium hydride) It reduces the carboxylic acid right down to an alcohol. You cant get the reduction to stop at the

aldehyde. E.g. CH3CH2COOH + 4[H] CH3CH2CH2OH + H2O Propanoic acid Propan-1-ol Carboxylic Acids Lesson objective: To know about carboxylic acids Success criteria: Identify the carboxylic acid functional group

Explain the physical properties of carboxylic acids, in relation to their boiling temperatures and solubility Explain how carboxylic acids can be prepared Explain the reactions of carboxylic acids with: - lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether -bases to produce salts Carboxylic Acids Questions Butane molecules and ethanoic acid

molecules have a similar number of electrons but butane is a gas at room temperature and ethanoic acid is a liquid. Why is this? Because ethanoic acid has hydrogen bonding but butane does not Carboxylic Acids Questions Carboxylic acids can be prepared by the oxidation of alcohols or aldehydes.

A suitable oxidising agent is acidified potassium dichromate (VI). Name a suitable dilute acid to acidify the potassium dichromate (VI) solution Sulfuric acid Carboxylic Acids Questions Carboxylic acids can be prepared by the oxidation of alcohols or aldehydes. Name the aldehyde that could be

oxidised to produce ethanoic acid. Ethanal Carboxylic Acids Questions Carboxylic acids can be prepared by the oxidation of alcohols or aldehydes. Write an equation to represent the production of ethanoic acid from ethanol. CH3CH2OH + 2[O] CH3COOH + H2O

Carboxylic Acids Questions Carboxylic acids can also be produced by the hydrolysis of nitriles in the presence of dilute hydrochloric acid. Write an equation to represent the production of ethanoic acid from ethanenitrile, CH3CN. CH3CN + H+ + 2H2O CH3COOH + NH4+ Or CH3CN + HCl + 2H2O CH3COOH + NH4Cl

Carboxylic Acids Questions Carboxylic acids can also be produced by the hydrolysis of nitriles in the presence of dilute hydrochloric acid. Give the reaction condition necessary for this preparation. Reflux Carboxylic Acids Questions Write an equation for the reaction between propanoic acid and calcium

carbonate and the name the salt produced. 2CH3CH2COOH + CaCO3 (CH3CH2COO)2Ca + H2O + CO2 Calcium propanoate Carboxylic Acids Lesson objective: To know about carboxylic acids Success criteria: Identify the carboxylic acid functional group Explain the physical properties of carboxylic

acids, in relation to their boiling temperatures and solubility Explain how carboxylic acids can be prepared Explain the reactions of carboxylic acids with: - lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether -bases to produce salts -phosphorus(V) chloride (phosphorus pentachloride)

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