3:7 iosmerism and carbonyl compouds (up to aromatic)

two types of sterioisomerism

Optical and geometric

What is a chiral carbon

What are two optical isomers called and why are they optical isomers

Carbon atom that has four different group attached to it.

Enantiomers and they are mirror images that can’t be superimposed

What do optical isomers do in terms of light

Rotate plane polarised light because they are optically active. One enantiomer rotates it in a clockwise direction, the other in an anticlockwise direction. - this is how you distinguish between two enantiomers

What’s a race mate

A race mate contains equal quantities of each enantiomer of an optically active compound. They don’t show any optical activity as they cancel out each others light-rotating effect. If you react two chiral things you often get a racemic mixture of a chiral product, that’s because there is an equal chance of forming each of the enantiomers.

What kinds of reactions produce race mates

Why?

Ones with planar bonds such as C=O or C=C bonds. reactions with the carbonyl group of aldehydes and unsymmetrical ketones are often enantiomers present as a racemic mixture

The nucleophile can attack from two directions, above or below the plane of the moelcules. Depending on high direction one of the enantiomers are formed. because the C=O is polar, there is an equal chance the nucleophile will attack form either directions and so equal amount of each enantiomer formed.

Example of an nucleophile attacking a carbonyl and what this reaction is called

Potassium cyanide will react with carbonyls by nucleophillic addition, producing hydroxynitriles.

1) potassium cyanide dissociated in water to form K+ ions and CN- ions : KCN → K+ + CN-

2) CN- group attacks partially positive carbon atom and donated a pair of electrons. A pair of electrons are transferred form one double bond to the oxygen and the oxygen becomes negatively charged and has a lone pair.

3) H+ iOS add to the oxygen to from a hydroxyl group, comes from acidified KCN or you a use HCN . If you use acidified KCN

HCN is weak so KCN is preferred

Risk of working with potassium cyanide and how to reduce risk

It is an irritant and extremely dangerous if ingested or inhaled. It can react with moisture to produce HCN which is a highly toxic gas. To reduce risk a person should wear gloves, safety goggles and a lab coat and perform the experiment in a fume cupboard.

Products when carboxylic acids react with carbonates

Products when carboxylic acids react with alcohols to form esters → esterification

Form carbon dioxide

H from COOH is removed and Na is put there instead (salt), the other products are HO (l) and CO2(g)

Form esters with a strong acid catalyst and heating the carboxylic acid with an alcohol. It’s called an esterification reaction and releases a water molecule so its also a condensation reaction.

Uses of esters

Sweet smelling so can be used in perfumes or to flavour things.

They are also polar liquids so lots of organic polar compounds will dissolve in them and they have low boiling points so they evaporate easily from mixtures.

Also used as plasticisers, and are added to plastics during polymerisation to make the plastic more flexible.

What is acid and base hydrolysis of an ester

Hydrolysis but use of an acid or alkali to speed it up. You get an alcohol wit both types but the second product is different,

Acid hydrolysis = splits the ester into an acid and an alcohol, under reflux with a dilute acid → such as hydrochloric or sulfuric acid. This reaction is reversible so needs a lot of water to push it to the right.

Base hydrolysis = refluxing the ester with a dilute alkali such as sodium hydroxide and you get a carboxylate ion and an alcohol. ( a carboxylate ions is a carboxylic acid without the H+)

What are fats and oils

Fatty acids are long chain carboxylic acids. They combine with glycerol to make esters. These esters of glycerol are fats and oils. The fatty acids can be saturated or unsaturated.

Animal fats have many saturated hydrocarbon chains, fit neatly together increasing VDW forces between them, so need higher temps to melt

Vegetable oils have unsaturated hydrocarbon chains, the double bonds mean gains are bent and don’t pack together well, decreasing the VDW forces between them, so they are easier to melt and liquids at room temp

How are oils and fats hydrolysed and what does it make

Hydrolyse vegatble oils and animal fats by heating them with sodium hydroxide. products is glycerol and a sodium salt (called SOAP)

The soap is a long-chain carboxylic acid with Na bonded instead of H in COOH

What is biodiesel

Mixture of methyl esters from fatty acids.

A methyl ester is made by reacting triesters with methanol, and using potassium hydroxide as a catalyst which makes glycerol and 3 methyl esters. You use 3 methanol molecules

Functional group of acyl chlorides

What dot hey react with and what are there products

What is common with all these reactions

-COCl end in -oyl chloride. They easily lose their chlorine

React with water - a vigourous reaction with cold water and produces a carboxylic acid and HCL

React with alcohols - a vigorous reactions at room temp and produced an ester and HCL. This reaction is a much easier and faster way to make an ester than esterification

React with ammonia - A violet reaction at room temp producing an amide and HCL

React with primary amines - A violet reaction at room temp to make an N-sub amide and HCL

Each time Cl is substituted by an oxygen or nitrogen group and misty fumes of HCl are produced

What is an acid anhydride

Made from two carboxylic acids in which both O-H sections bond, and loses a water molecule, instead of naming with acid use anhydride instead. They have similar reactions to acyl chlorides but they are just less vigorous and instead of HCl as a product you get a carboxylic acid formed.

What reactions are acyl chloride reactions

They are nucleophilic addition elimination reactions. In acyl chlorides both eh chlorine and oxygen draw electrons tot themselves so the carbon has a slight positive charge, meaning to easily attacked by nucleophiles.

Lone pair on O or N depending on what is reacting is attracted to the C so arrow from lone pair to the C. Then an arrow from one of the bonds in the doubled bonded O to the O itself which will form a negative O with a lone pair of electrons. In the next diagram the negative O draws its electrons back to the bond and the Cl removes itself. In the final drawing the O or N that has bonded is positive so the Cl- ion with a lone pair is drawn to one of the H on the molecule and O draw the bond between the O and the H back towards itself. Final molecule is made

What is ethanoic anhydride used for, how is it made

And why one reactant over the other in industry

manufacture of aspirin as its an ester and it is made by reactive salicyclic acid with enthanoic anhydride or ehthanoyl chloride.

Ethanoic anhydride is used in industry because its cheaper, safer as its less corrosive, reacts more slowly and doesn’t produce dangerous hydrogen chloride fumes like ethanoyl chloride does

Separation technique to remove water soluble impurities from a product that is insoluble

Pour mixture into a separating funnel and add water. Shake the funnel and allow to settle. It will form an organic layer and an aqueous layer(on the bottom) that is immiscible (don’t mix). Open the tap and run each layer off into a separate container.

How to separate product and impurities if they are both soluble in water

Solent extraction that you can use. You take an organic solvent in which the product is more soluble in water. You add it to the impure product solution and shake well. The product will dissolve into the organic solvent, leaving impurities dissolved in the water. The solvent containing the product can the be run off using the separating funnel.

How to remove water from a product

Dryin it. Even Seperation to purify a product, it will still contain trace amounts of water. Add anhydrous salt such as magnesium sulfate (MgSO4) or calcium chloride (CaCl2) the salt is used as a drying agent and will bind to any water present to become hydrated. When you first add the salt to the organic layer it will clump together. You keep doing the drying agent until it disperses evenly when you swirl the flask, then filter using filter paper.

Another general way to remove impurities after product has been separated from other products

washing - as product can be contaminated with leftover reagents or unwanted side products. For example aqueous sodium hydrogen carbonate can be added to an impure product in solution to remove acid from it. The acid reacts with sodium hydrogen carbonate to give CO2 gas.

What is distillation and what is it used for

Separates out volatile liquids with different boiling points. It works by gently heating a mixture in a distillation apparatus. The substances will evaporate out the mixture in order of increasing boiling point

Apparatus with a round bottom flask supplied with heat, a thermometer and a condenser at a downslope angle with a conical flask submerged in ice. Mae sure to use an electric heater because most organic chemicals are flammable .

How to purify organic solids

Recrystalaition

Dissolve solid in hot Solent to make a saturated solution - max possible amount of solid is dissolved. Then let it cool, and as it cools, the solubility of the product falls. When it reaches the point where it can’t stay in solution it forms pure crystals

1)Add hot solvent but keep saturated so don’t add too much

2) filter through a heated funnel to remove any insoluble impurities

3) Leave to cool down slowly and crystals will form

4)Remove liquids containing soluble impurities from the crystals by filtering the mixture under reduced pressure and using a Büchner funnel

5) wash the crystals with ice cold solvent to remove any soluble impurities for their surface and leave your purified crystals to dry

How to see if a solid is pure using melting or boiling points

If impure, melting point is lowered and the boiling point is raised. If they are very impure, melting and boiling points will occur across a wide range of temperatures

Use a meting point apparatus to accurately determine melting point of an organic solid. Place small sample in a glass capillary and place it in heating element. Raise temp until it melts, record when it melts ands its melting range. Look up the melting point of a substance in data books and compare to measurements.