Unit 2 Flashcards
Functional Group of Alcohols
O-H (Hydroxyl)
General formula for Alcohols
CnH2n+2O
Compounds in the same homologous series
- Same functional group
- Same general formula
- Similar chemical properties
- Gradual change in physical properties
General formula for Alkanes
CnH2n+2
General formula for Alkenes
CnH2n
Functional group of Alkenes
C=C (Carbon to carbon double bond)
Test to see if a compound is unsaturated
Bromine water and it goes colourless
General formula for cycloalkanes
CnH2n
Why are alcohols soluble in water?
Hydrogen bonds form between the alcohol molecules and O-H groups (Like dissolves like)
Why do alcohols have a higher bpt than hydrocarbons with a similar mass?
Hydrogen bonds between the alcohols need to be broken which takes much more energy than to break the ldf between hydrocarbons
General formula for carboxylic acids
CnH2nO2
General formula for esters
CnH2nO2
Functional group for esters
Ester link or carboxylate (-COO-)
Condensation Reaction
When the molecules react to produce a larger molecule and another small molecule (Like water)
Functional group for Carboxylic acids
Carboxyl (COOH)
What reactions do alcohols and carboxylic acids to become esters
Condensation or Esterification
What functional groups react to form the ester link
Hydroxyl and Carboxyl
Advantages of using concentrated sulphuric acid when making an ester
- Catalyst
- Absorbs water formed
Why’s it important in esterification that concentrated sulphuric acid absorbs water
Prevents the reverse reaction occurring
Purpose of paper towel in making an ester
Acts as a condenser to prevent volatile gases escaping (cooling them down)
Why’s the reaction mixture heated in a water bath in Esterification
To increase the rate of reaction, a Bunsen can’t be used as the reaction is flammable
Why’s the mixture poured into sodium hydrogen carbonate in Esterification?
To neutralise the concentrated sulphuric acid catalyst and any excess carboxylic acid
Why are alcohols and carboxylic acids soluble in water whereas esters are insoluble in water?
Alcohols are very soluble due to the polar O-H groups that form H-bonds with water. Carboxylic acids are the same but due to the COOH group. Esters are insoluble as the molecule is mostly non-polar and can’t form H-bonds with water
Uses for Esters
Adhesives, Ink or Paint
How does esters dissolve into other molecules?
As esters are non-polar, the molecules they dissolve into are also non-polar
“Like dissolves like” Ldf form
Hydrolysis
Large molecules are broken down into smaller molecules by the reaction with water
What happens when esters are hydrolysed?
They produce the parent carboxylic acid and parent alcohol
Equation of reversible esterification
Acid + Alcohol ↔ Ester + Water
Acid- Catalysed Hydolysis
Heating the ester with dilute HCL or H2SO4 provides H+ ions which catalyse the reaction
Alkaline Hydrolysis
Alkali’s often are used to catalyse the reaction and mixture heated under reflex
Products of Alkaline Hydrolysis
Alcohol and Carboxylic Acid
Advantage(s) of Alkaline Hydrolysis
- Not reversible
- Higher Yield
- Easier to separate the products
What do fats and oils provide our body with
- Energy
- A more concentrated source of energy than carbohydrates
What are fats and oils
Naturally occurring esters of the alcohol glycerol and long carboxylic chains
Long carboxylic chains
“Fatty Acids”
Structure of Glycerol
.......H ........I H - C - O - H ........I H - C - O - H ........I H - C - O - H ........I ........H
Structure of fat or oil
........H........O ........I...........II H - C - O - C - R1 ........I...........O ........I............II H - C - O - C - R2 ........I............O ........I.............II H - C - O - C - R3 ........I .......H
What functional group is in fats and oils and how many of them?
3 Ester Links
Other name for Glycerol
Propane-1,2,3-triol
Equation for making fats and oils
3 fatty Acids + Glycerol -> Fat or Oil
Why has glycerol got a high bpt and viscosity
- Glycerol has 3 O-H groups allowing lots of H-bonds to form between the glycerol molecules
- As lots of energy is needed to break the hydrogen bonds
Fatty Acid Diagram
…………….O
……………..II
VVVVVvC-O-H
How to change an oil to a fat (Summarise)
- Hydrogenation (Addition of Hydrogen)
- In the oil the C=C is changed to C-C bonds making the molecules more saturated and more linear
- Molecules pack more closely, leading to stronger ldf between chains
- More energy to break, leading to a higher mpt and bpt
Why oils have a lower mpt than fats
- Saturated hydrocarbons so not linear
- Less energy to break, leading to a lower mpt and liquid oil
- Molecules don’t pack closely, weaker ldf between chains
At room temperature, what state is fats and oils in?
Fats- Solid
Oils- Liquid
How is triglyceride formed
3 moles of fatty acids, 1 mole of glycerol
Diagram of a fat molecule
.............I/\/\/\/\/\ .............I \/\/\/\/\/I .............I .............I/\/\/\/\/\
How will the close packing of fat molecules affect the strength of the ldf
Stronger
How will the close packing of fate molecules affect the mpt and bpt
Higher
Soap
Salt of a fatty acid
How are soaps produced?
By alkaline hydrolysis of fats and oils
Emulsifying Regeants
Chemicals which can make oil and water become permanently mixed to produce a stable emulsion
Examples of “emulsifying regeants”
Soaps and Detergents
How do soaps and detergents act as emulsifying regeants
Soap molecules have a long non-polar hydrocarbon chain ‘tail’ which is readily soluble in non-polar (Hydrophobic) compounds and a polar ionic carboxylate ‘head’ which is water soluble (Hydrophylic)
Explain the cleansing action of soap
During cleaning, the hydrophobic tails of the soap dissolve in the droplet of the grease, whilst the hydrophylic heads face out into the surrounding water, resulting in ball like structures
‘Hard Water’
Water that contains a high concentration of calcium and magnesium ions which make it hard to form a lather of soap- a white scum forms instead
Scum
The name given to the precipitate when the Ca2+ and Mg2+ ions in hard water and react with the fatty acid part of the soap
Benzene Ring
C6H6
Emulsions in food
Mixtures of oil and water
Why would an emulsifier be used?
To prevent oil and water components separating into layers
How is emulsifiers used in food commonly made?
By reacting edible oils with glycerol to form molecules in which either one or two fatty acid groups are linked to a glycerol backbone rather than the three normally found in edible oils
What do we need proteins for?
Growth and Repair
Proteins are the major structural materials of ….
Skin, tissue and muscle (Meat)
Two types of proteins
Fibrous and Globular
Structure of fibrous proteins
- Long, thin structure
- Molecular chains are interwoven to form multi-strand cables due to the intermolecular (Hydrogen) bonding between the carboxyl and amino groups in adjacent polypeptide chains
Properties of Fibrous proteins
- Insoluble in water
- Fairly stable to changes in pH and temperature
- Tough
- Unreactive
What are fibrous proteins used as?
Structural proteins
Where can fibrous proteins be found in the body?
- Skin
- Hair
- Muscle (Meat)
What’s the structure of globular proteins
- Consists of spiral chains which are folded into compact units by hydrogen bonds
- The hydrogen bonds form between the carboxyl and amino groups of the amino acids in the same polypeptide chains to produce spirals
Properties of globular proteins
- Soluble in water
- Sensitive to pH changes
- Changes in temperature
- Highly reactive
What are globular proteins involved in?
The maintenance and regulation of life processes including enzymes, hormones (e.g. insulin) and haemoglobin
The ‘active site’ in globular proteins
Important functional groups from different parts of the polypeptide chain and brought together
Enzymes
- Proteins
- Biological Catalysts
Enzymes are _____ to particular chemical reactions
Specific
Certain sequences of amino acids form a region known as the ______
Active Site
‘Lock and Key’ Method
The shape of the active site allows specific reactants known as substrates to attach
The enzymes active site and the substrate must have a ______
Complementary shape
What functional group(s) are in amino acids
- Amino Group(-NH2)
- Carboxyl Group(-COOH)
What molecules do amino acids contain
Hydrogen, Carbon, Nitrogen and Oxygen
How are proteins formed
By combining amino acids to form long chain molecules of maybe several thousand amino acid units long (condensation polymers)
What is formed when amino acids join together
- An amide link(or peptide link)
- Water
How many amino acid units does a tripeptide have?
3
What’d a longer chain of amino acids called….
Polypeptide
How many different types of amino acids would be produced during hydrolysis of this section of a polypeptide chain
3 different types
A primary alcohol (Diagram)
.......O - H ........I H - C - H ........I ........R
Secondary Alcohol (Diagram)
.......O - H ........I R - C - H ........I .......R1
Tertiary Alcohol (Diagram)
.......O - H ........I R - C - R3 ........I ........R1
What happens when proteins are heated?
The hydrogen bonds between the chains are broken, causing the proteins to change shape
How does water soluble vitamins and flavour molecules dissolve in water?
The water soluble vitamins and flavour molecules have polar functional groups like OH, COOH, NH2, C=O, COO which can form hydrogen bonds with water
How does fat soluble vitamins and flavour molecules dissolve in oil?
The fat soluble vitamins and flavour molecules have non-polar fuctional groups like long hydrocarbon chains that can form ldf with oils
Primary (1°) alcohol
The carbon which carries the -OH group which is only attached to one carbon atom
Secondary (2°) alcohol
The carbon with the -OH group attached is joined directly to two carbon atoms
Tertiary (3°) alcohol
The carbon atom holding the -OH group is attached directly to three carbon atoms
Combustion of Alcohols
Alcohols burn in oxygen and air to produce carbon dioxide and water
The word equation for combustion of alcohol
Alcohol + Oxygen -> Carbon Dioxide + Water
What colour change happens when acidified dichromate solution is added to:
a) 1° alcohol b)2° alcohol c) 3° alcohol
A & B= Orange to green
C= No change
What happens when a)1° alcohol b) 2° alcohol is heated with hot copper oxide?
A= Goes red (Meaning an acid is formed) B= No significant change
What product(s) are produced when a primary alcohol is oxidised
Aldehyde -> Carboxylic Acid
What product(s) are produced when a secondary alcohol is oxidised
Ketone
What product(s) are produced when a tertiary alcohol is oxidised
No product (No reaction)
What is formed when fats and oils are hydrolysed
Fatty Acids and Glycerol
Name of the molecule with three hydroxyl groups
Trihydric Alcohol or Triol
Functional group of aldehyde and ketone
Carbonyl Compound
General formula of Aldehydes and Ketones
CnH2nO
What happens when a)Aldehyde b)Ketones are reacted with Benedicts solution
A= Blue to orange with a brick red precipitate B= No change
What happens when a)Aldehydes b)Ketones are reacted with Tollen’s regeant
A= Silver mirror is formed B= No change
What happens when a)Aldehydes b)Ketones are reacted with acidified dichromate
A= Orange to green B= No change
Antioxidants
- Molecules which will prevent oxidation reactions taking place
- Reducing agents and get oxidised themselves
Free radical scavengers
They can prevent oxidative damage to molecules by transferring electrons to substances known as free radicals
Free Radical
A substance that has unpaired electrons
What can affect the Vitamin C Content of food
- Ripeness of fruit
- Age of fruit
- Variety of fruit
- How food is processed
- How it’s cooked
What’s the reaction when carboxylic acids are mixed with lithium aluminium hydride
It’s reduced in stages to the original aldehyde and alcohol
Reduction reaction of a carboxylic acid
Involves a decrease in the oxygen to hydrogen ratio (Because oxygen is lost or hydrogen in gained)
What can alkanones be reduced to?
2° Alcohols
Neutralisation
The neutral ion in the base replaces the hydrogen of the carboxyl group in the acid
Essential Oils
Hydrophobic liquids containing mixtures of volatile aroma compounds that evaporate easily in air giving distinctive fragrances
What do essential oils contain
A mixture of organic compounds, with aromatic molecules
Where are essential oils extracted from?
From plant material, need to obtain the liquid before it evaporates
Steam distillation
A mixture of oil and water, but because the two mix, they’re easily separated
Why in the condenser of steam distillation does there need to be a lot of the organic compounds (e.g. orange peel)
So that the steam must pass through it to extract the oil
What’s an important component in essential oils
Terpenes
How are terpenes formed
By joining together isoprene units
General formula for terpenes
(C5H8)n
Why would isoprene units be linked together ‘head to tail’
To form linear chains or arranged to form rings
How can you reduce photo oxidation (Due to light)
It can be stored in brown bottles
What’s produced when terpenes are oxidised within plants
Some of the compounds responsible for the distinctive aroma of species
Ultraviolet Radiation (UV)
A high energy form of light, present in sunlight
Sun- Block
Prevents UV light reaching the skin
What can exposure to UV light result in?
Molecules gaining sufficient energy for covalent bonds to be broken
What does UVA and UVB cause?
The breakdown of collagen, creating substances called free radicals that inhibit the natural repair of the skin
3 Stages of a free radical chain reaction, initiated by UV light
-Initiation, Propagation, termination
Initiation
UV Provides energy for the homolytic fission of the covalent bond between the halogen atoms to form two free radicals
Propagation
Free radicals collide with other molecules to give a stable product and another free radical
How would an explosion occur in the propagation stage?
A fast chain reaction occurs because while free radicals are being regenerated during the propagation stage, new free radicals are being produced in the initiation stage
Termination
Free radicals are used up when they collide with each other to form a stable molecule
