C26 compounds with a carbonyl group

• aldehydes and ketones contain a carbonyl group, which consists of a C=O, carbon-oxygen double bond
• aldehydes have the C=O on the end of the carbon chain, ketones have the C=O in the middle of the carbon chain
• aldehydes have the suffix -al and ketones have the suffix -one
• the carbonyl group is strongly polar because O is much more electronegative than C, so there is a permanent dipole-dipole force between these atoms
• aldehydes and ketones have higher boiling points than alkanes due to the polar carbonyl group, but lower boiling points than alcohols due to lack of hydrogen bonding
• compounds with the carbonyl group mostly undergo nucleophilic addition reactions, but they also undergo redox reactions
• in nucleophilic addition, a common nucleophile would be NaCN or KCN because HCN is too toxic if it escapes, then dilute hydrochloric acid is added so there are hydrogen ions in the solvent
• the product of nucleophilic addition would be a hydroxynitrile
• the process of nucleophilic addition is: C=O is polar as C is positive and O is negative, negative nucleophile is attracted to positive carbon, C=O becomes C-O, O now has a lone pair so is negative, the H+ ions from the solution are attracted to the negative O creating an -OH
• aldehydes are oxidised to carboxylic acids, ketones cannot be oxidised
• a common oxidising agent is acidified potassium dichromate
• oxidation is used to distinguish between aldehydes and ketones in two ways, the fehling's test and the silver mirror test
• for a fehling's test, add fehling's solution, heat, positive result is a colour change from blue to brick-red precipitate
• for a silver mirror test, add tollens' reagent, heat, positive result is a silver mirror forming
• positive results in the fehling's or silver mirror tests mean the sample is an aldehyde not a ketone, because the reagents oxidise the sample, and ketones are not easily oxidised
• both aldehydes and ketones can be reduced to alcohols, aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohols
• the process of reduction is the same as nucleophilic addition, with the hydride ion as a nucleophile, and then protons from the solution
• the functional group for carboxylic acids is -COOH which is made up of a carbonyl group and a hydroxy group
• carboxylic acids have the suffix -oic acid
• carboxylic acids can form hydrogen bonds with water, which makes them soluble in water, but solubility decreases the longer the chains get
• carboxylic acids can also form hydrogen bonds with each other which gives them relatively high melting points
• esters can be formed by reacting a carboxylic acid with an alcohol
• to name esters use the parent names, the alcohol root becomes the first half ending -yl, and the carboxylic acid root becomes the second half ending -oate
• short chain esters have pleasant fruity smells, so are often used in flavourings and perfumes, but also as solvents and plasticisers, whereas long chain esters are used as fats and oils
• the carboxylic acid group is polarised, which means the C is open to attack from nucleophiles, and the O is open to attack from electrophiles, and the H may be lost as protons
• carboxylic acids undergo 4 types of reaction: nucleophilic addition, loss of a proton, reactions with group 1 metals, and reactions as acids
• in nucleophilic addition of a carboxylic acid, a nucleophile attacks the positive end of a C=O group which then gains a hydrogen to form an -OH group
• in loss of a proton from a carboxylic acid, if the proton is lost from the -OH group, a negative carboxylate ion is formed, which is stable as the charge is shared over all of it
• in reactions of carboxylic acids and group 1 metals, the carboxylic acids are weak but strong enough to react with compounds such as sodium hydrogencarbonate
• in reactions of carboxylic acids as acids, they form ionic salts with more reactive metals, alkalis, metal oxides, or metal carbonates, called carboxylates
• the ester group is polarised as it contains the carbonyl group then also an R group
• esters undergo hydrolysis reactions
• in hydrolysis reactions of esters, water acts as a weak nucleophile, requiring an acid catalyst, which creates an equilibrium mixture, and produces alcohols and carboxylic acids
• the proper name of glycerol is propane-1,2,3-triol
• glycerol creates esters which are used as animal and vegetable oils and fats
• oils and fats are made up of glycerol and three carboxylic acid fatty acid chains, these are called triglycerides
• hydrolysing fats and oils in acid conditions produces a mixture of glycerol and fatty acids
• hydrolysing fats and oils in alkaline conditions produces a mixture of glycerol and soaps
• the acyl group contains an R group and a carbonyl group
• acylation is the process by which the acyl group is added to a molecule