Whats in a medicine- Chemsitry

When naming alcohols what is the endig

-ol

How to name alcohols

1. Find the longest carbon chain

2. Use the alkane name for the chain length e.g. meth,eth,prop,but,pent and change the ending to -ol

3. Number the carbon chain so the -OH group has the lowest number.

4. If the -OH group isn’t on the first carbon add the number before the -ol e.g. propan-2-ol

5. Identify any alkyl groups e.g. methyl,ethyl using di or tri if mutiple

6. Write alphabetically

How to write a molecular formula

You can only write each atom once so not showing functional groups

E.g. C4H10O instead of C4H9OH

Full structural formula of ethanol

Include every bond including the O-H

What is a phenol

An -OH group bonded directly to a benzene ring

Physical properties of alcohols

1. The hydrocarbon chain is non-polar and the -Oh group is polar as oxygen is a lot more electronegative than hydrogen.

2. This increases the boiling point of alcohols compared to alkanes with similar Mr as to boil an organic liquid you need to overcome intermolecular bonds (between molecules) which are usually weak.

3. Due to the polar _OH group there are strong attractions between molecules because of hydrogen binding which require more energy to be overcome.

How well do alcohols mix with water

Alcohol with small molecules mix well with water as hydrogen bonds form between the two but as the non polar hydrocarbon chain gets longer the influence of the polar -OH on properties decreases.

So longer chain alcohols mix less well with water

What are ethers

Structural isomers of alcohols.

The oxygen in ethers is bonded to two carbons so is in the middle of the carbon chain

Physical properties of ethers

1.As they have no -OH group there is no hydrogen bonding between molecules so they have inch lower boiling points than alcohols of the same Mr

2. They dont mix with water ( no hydrogen bonding between molecules

What is an aldehyde

1. It has the functional group c=o and a hydrogen on the C

2. It is often written as R-CHO

3. It ends in -al

What is a ketone

1. Ketone has the functional groups C=O with the C attached to 2 R groups

2. It is often written as RCOR

3. It ends in -one

What is a carboxylic acid

1. It has the functional group C=O with the C also attached to an -OH

2. It is often written as RCOOH

3. It ends in -oic acid

Out of ketone, aldehyde and carboxylic acid which molecules have hydrogen bonding and why

Only carboxylic acids because they have an -OH group

How to classify alcohols

The number of carbons the carbon bonded to an -OH group is bonded to.

How to classify a primary alcohol

The carbon with the -OH group is bonded to one other carbon

Oxidation of alcohols

Alcohols are heated with acidified potassium dichromate (VI)solution/ K2Cr2O7/H+

This is orange ad when oxidising something it itself is reduced to green Cr3+

Oxidation of primary alcohols too aldehydes

1. You need to limit oxidation by using the minimum amount of oxidising agent and distilled water products out of the mixture as they form.

2. Aldehyde will distill over rather than any remaining alcohol reactant, or any carboxylic acid which moleculesd made by further oxidation as it has thee lowest boiling point

3. We know this because alcohols and carboxylic acids have an -OH group so can form hydrogen bonds between molecules but aldehydes cannot make hydrogen bonds so less energy is required to overcome intermolecular bonds.

Balanced equations for the oxidation of a primary alcohols too to an aldehyde

Diagram of distillation

Oxidation on primary alcohols too carboxylic acids

1. Need oxidation to go as far as possible so use excess oxidising agent and heat the mixture under reflux to give plenty of time for maximum oxidation

Balanced equation of oxidation of primary alcohols too to carboxylic acid

What is reflux and draw a diagram

Reflux is boiling a liquid reaction mixture under a vertical condenser so vapour continually condenses and drips back in rather then being lost

Oxidation of secondary alcohols with an equation

Oxidised in 1 stage giving a ketone and cannot be oxidised further s the c-c bond would have to break so alcohol and oxidising agent are heated under reflux

Oxidation of tertiary alcohols

1. Cannot be oxidised as would need to be c-c bond to break so if heated with acidified potassium dichromate it remains orange

Dehydration of alcohols

Need to pass vapour of the alcohol over a heated catalyst of aluminium oxide

OR

Heat under reflux with concentrated sulfuric acid (dehydrating agent)

Loss of a water molecule so -OH in alcohol leaves with H from molecule next door producing an Alkene.

Draw the apparatus for a heated catalyst of aluminium oxide

Draw the equation when Bután-1-ol vapour is passed over heated aluminium oxide catalyst

What type of reaction is a dehydration reaction

An elimination- where a small molecule is removed from a larger molecule giving an unsaturated molecule

Nucleophilic substitution of alcohols too make haloalkanes

Alcohols react with halide ions in the presence of a strong acid

Purification of liquid haloalkane

1. Mixture is separated into a separating funnel where 2 liquid layers separate

2. There s a less dense upper layer and a more dense lower layer.

3. The lower layer is run off and if it I the aqueous layer it is discarded.

4. With the organic layer back in the separating funnel, sodium hydrogen carbonate solution is added and mixture is shaken removing any acid

5. This is repeated until no more co2 forms

6. Organic layer is shaken with water to remove remaining NaHCO3

7. Organic product is run into a clean flask and a drying agent is added with swirling e.g. Anhydrous sodium sulfate

8. Then distilled and collect only the liquid that distills at the right temperature

What is an ester

Structure with a C=O with the carbon bonded to an oxygen

Many smell like flowers and fruits used in perfumes

How do you make esters

1. From an alcohol and a carboxylic acid in a reversible reaction making ester and water

2. Conditions are heat under reflux with an acid catalyst ( conc H2SO4 or conc HCl

Draw the formation of propyl ethanoate

Draw a spider diagram of the reaction of alcohols

Which three molecules have an -OH group

1. Alcohols

2. Phenols

3. Carboxylic acids

Table of acid behaviour for alcohols, water, phenols, and carboxylic acids

Draw reaction of a carboxylic acid and a base

When an acid reacts the H+ gets replaced by a metal ion giving a salt. Salts have ionic bonding and Na+ is attracted to the O- by electrostatic attraction

Draw reaction between phenol and a base

How does the reaction of a phenol and base affect the solubility of a phenol

1. Phenol is solid so not very soluble as hydrophobic ring prevents hydrogen bonding

2. Do dissolve in alkali as it becomes the salt which is ionic so more soluble as forms ion dipole bonds with water

Draw reaction of carboxylic acid and carbonate

Forms salt after and CO2 and as gas given it will fizz-test for carboxylic acid

Why is there a difference in acid strength of alcohols, phenols, and carboxylic acids

Acid strength depends on the position of equilibrium.

If it lies further to right the acid is better at donating H+so is a stronger acid

How far right it lies depends on how stable the anion is. If negative charge is delocalised it makes thee anion more stable

Test for a phenol

Iron (III) chloride test

It is orange but if added to a phenol group the solution turns deep purple

Summary table of -OH reactions

How can esters be made from phenols

Phenols are less reactive than alcohols so are reacted with something more reactive then a carboxylic acid so:

acyl chloride

OR

Acid anhydride

Draw reaction of phenol and acid anhydride ( ethanoic anhydride)

How else can acid anhydride make an ester

When reacted with alcohol

How to purify an organic solid

1. Solvent is chosen carefully as needs to be one that the desired product dissolves well in hot by not well when cold so products crystalline when cooling

2. Impure solid is dissolved in the minimum amount of hot solvent making a saturated solution and any soluble impurities will dissolve

3. Insoluble impurities are removed by filtering while it is still hot

4. 4. Leave the filtrate to cool and as it owes the solid becomes less soluble in the solvent so starts to crystallise out. Small amount of solid will stay in solution as well as any soluble impurities.

5. Collect crystals by vacuum filtration which will remove soluble impurities as they will be in te filtrate whereas product crystals will be on filter paper

6. Wash crystals with small amount of cold solvent

7. Dry crystals in open air or in oven with temps below melting point

8. The purity of the solid can be checked by doing a melting point determination

How to do a melting point determination

1. One end of a capillary tube is sealed by melting the glass I a hot Bunsen flame

2. Small amount of solid is put into the bottom and the tube is put into melting point apparatus

3. Temperature slowly increases

4. Temp recorded at the Start and finishing melting points

5. Pure solids melt sharply within 0.5 degrees of the expected but impurities lower the melting point increasing the range of temperatures

What is chromatography used for

To separate and identify compounds in a mixture or to purify an organic compound

In chromatography what is the mobile and stationary phase

Mobile-the solvent moving up the plate

Stationary-filter paper in page chromatography but usually the thin layer of silica spread on a plastic sheet

How is a TLC done

1. Daw a pencil line 1cm from the bottom of the TLC plate/paper

2. Dissolve test mixture in a small amount of solvent and spot them in different marked places on your pencil line

3. Stand the plate in a beaker containing small amount of chromatography solvent ensuring solvent level is below line with spots

4. Cover the beaker with a lid and allow solvent to travel up the plate

5. Once near the top remove plate and mark the solvent front

6. Allow to dry

7. If spots are colourless locate them by: viewing under UV lamp, use iodine crystals, spray with locating agent

8. Pure substances only have 1 spot

9. Use Rf value which is distance travelled by pot divided by distance solvent from travelled

How does infra red spectroscopy work

Each compound has its own unique infra red spectrum. Infrared of gradually changing frequency is shone at the sample. When a frequency is reached which corresponds to vibrational energy change for one of the bonds, the molecule absorbs that frequency of infra red and a peak appears on the spectrum

On an infra red spectrum what is frequency measured in

Wave number cm-1

C=O in infra red spectroscopy

Strong peak at 1700cm-1 and almost always the strongest peak

O-H in infra red spectroscopy

Broad peak very far left of the spectrum

Not to be mixed with C-H which is a sharp peak or a group of sharp peaks

In carboxylic acids the OH group isn’t as far left as in alcohols and phenols so can crash into C-H peak

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