higher chemistry unit 2

alkanes

saturated hydrocarbons (C to C single bond)

alkenes

unsaturated hydrocarbons (C to C double bonds)

cycloalkanes

saturated hydrocarbons arranged in a ring structure. (c-c)

cycloalkanes

unsaturated hydrocarbons arranged in a ring structure. (C=C)

alkynes

unsaturated hydrocarbons ( C to C triple bonds)

carboxylic acids

contains a carboxyl group (-COOH)

alcohols

contains a hydroxyl groups (-OH)

methyl

CH₃

ethyl

C₂H₅

meth-

1 carbon

eth-

2 carbons

prop-

3 carbons

but-

4 carbons

pent-

5 carbons

hex-

6 carbons

hept-

7 carbons

oct-

8 carbons

non-

9 carbons

isomers

compounds which have the same molecular formula but different structural formulas

isomer steps

1. shorten the carbon chain and add a branch

2. move functional group

3. alkenes are isomers of cycloalkanes

hydration equations

reactions of carboxylic acids

1. metal oxide+carboxylic acid→salt+water

2. metal hydroxide+carboxylic acid→salt+water

3. metal carbonate+carboxylic acid→salt+water+carbon dioxide

saturated

contains C-C bonds

unsaturated

contains C=C bonds

what can C=C take part in

addition reactions

test for unsaturation

rapidly decolourise bromine solution

primary alcohol

hydroxyl group is attached to a carbon attached to one carbon

secondary alcohol

hydroxyl group is attached to a carbon attached to 2 other carbon

tertiary alcohol

hydroxyl group is attached to a carbon attached to 3 other carbon

diol

alcohols containing 2 hydroxyl groups (OH)

triol

alcohols containing 3 hydroxyl groups (OH)

esters

molecule containing an ester link

ester link

O
I I
O - C

how are esters formed

by a condensation reaction of an alcohol and a carboxylic acid

use of esters

commonly used as fragrances as many have a fruity pleasant smell

what is glycerol known as?

propan-1,2,3-triol

Explain fully why fats have higher melting points than oils.Explain fully why fats have higher melting points than oils.

• Fats are more saturated

• they can pack together more closely

• Stronger LDF between the molecules

what are fats and oils?

• a concentrated source of energy

• they are essential for the transport and storage of fat-soluble vitamins in the body

fats

• solid at room temperature (high mp/bp)

• more saturated/ less unsaturated

• fat molecules pack closely together

• stronger LDFs which need to be overcome

oils

• liquid at room temperature (low mp/bp)

• less saturated/ more unsaturated

• oils can’t pack closely together due to kinles in the chain

• weaker LDFs which need to be overcome.

soaps

water-soluble ionic salts

soaps structure

• ionic head, which dissolves in water and is hydrophillic so is water soluble

• hydrophobic tail, which dissolves in non polar substances e.g. oil and is hydrophobic so is non water soluble

use of soap

• hydrophobic tail dissolves in oil

• hydrophilic head dissolves in water

• agitation causes micelles to form which repel eachother and they are suspended in the water until it drains away.

soapless detegent

• used in areas with hard water (high metal ion concentration)

• prevents scum from forming

emulsions

contains small droplets of one liquid dispersed in another liquid. Eg. oil and water

emulsifiers

can be used to prevent non polar and polar liquids from separating into layers

emulsifiers for use of food can be made by?

reacting edible oils with glycerol.

what are proteins?

the major structural materials of animal tissue and are also involved in the matainance and regulation of life processes

what are enzymes?

a protein that acts as a biological catalyst

amino acids

building blocks that make up a protein molecule, which contain an amino group, —NH2, and a carboxyl group, —COOH.

proteins are made by?

many amino acid molecules linked together by condensation reactions. In these reactions, the amino group of one amino acid and the carboxyl group of another amino acid join, with the elimination of water.

link between two amino acids

peptide link/ amide link

essential amino acids

the body cannot make these amino acids so they must be acquired from the diet

proteins which fulfill different roles in the body are formed by

linking together different sequences of amino acids

denaturing causes

• low pH

• high temperature

what happens when a protein denatures?

• changes shape

• intermolecular forces/hydrogen bonds break

During digestion, enzyme hydrolysis of protein produces

amino acids

For cabin compounds: oxidation and reduction

oxidation: an increase in the oxygen to hydrogen ratio

reduction: decrease in the oxygen to hydrogen ratio

oxidisation of primary alcohol

• Hot copper(II) oxide or acidified dichromate(VI) solutions can be used to oxidise primary alcohols to aldehydes and then to carboxylic acids

hot copper (II) oxide: color change

black→brown

acidified dichromate: colour change

orange→green

oxidisation of secondary alcohol

Hot copper(II) oxide or acidified dichromate(VI) solutions can be used to oxidise
secondary alcohols to ketones

oxidisation of tertiary alcohols

no further oxidisation

fehlings: colour change

blue→brick red

tollens: colour change

colourless→silver mirror

what defines a aldehydes

a carbonyl group and a hydrogen directly attached

what defines a ketone

a carbonyl group

many flavor and aroma molecules are?

aldehydes

Oxygen from the air causes the ___ of food?

oxidisation

oxidisation of edible oils gives food a bad taste

a rancid flavor

antioxidants

are substances that prevent unwanted oxidation reactions occuring, helping to maintain flavor and freshness in food.

essential oils

are concentrated extracts from plants that capture their scent and flavor

what are the key parts of an essential oil

terpenes

what is a terpene

unsaturated compounds formed by joining isoprene units

draw an isoprene

UV light causes

• sun burn

• aging skin

how are free radicals formed

when UV light breaks bonds

what are free radicals

atoms or molecules that are highly reactive due to the presence of unpaired electrons

what are free radical scavengers

molecules that react with free radicals to form stable molecules

3 steps of the free radical chain reactions

Initiation, propagation, termination.

Initiation, propagation, termination example

CH₄+Br₂→CH₃+HBr

1. Br₂→Br^*+Br^* initiation

2. CH₄+Br*→HBr+CH₃* propagation

3. Br*+Br*→Br₂ termination