Unit2 Flashcards
How are alcohols produced
Fermentation
What is fermentation
Enzymes convert carbohydrates (glucose) into ethanol and carbon dioxide
To meet the market production, ethanol is made by…
The catalysed hydration of ethene
What makes a Primary alcohol
Two hydrogen atoms bonded to the carbon atom, bonded to the oh hydroxyl functional group
(Exception is methanol )
A primary alcohol is equivalent to…
One alkane with one of its end hydrogens replaced by an hydroxyl functional group
Methanol and ethanol do not have…
Isomers that are alcohols
In a secondary alcohol…
Only one hydrogen atom is bonded to the carbon atom bonded to the hydroxyl functional group
Define a tertiary alcohol
The carbon atom bonded to the hydroxyl functional group has no hydrogen bonded to it
Carboxylic acids contain the functional group…
CooH
Carboxylic acids are formed
in the two stage mild oxidation of primary alcohols
Primary ➡️aldehyde➡️carboxylic acid
Ox Ox
Methanoic acid
Formic acid
HcooH
Ethanoic acid
Vinegar
CH3CooH
Propanoic acid
Ch3Ch2COOH
General formula for carboxylic acids
CnH2n-1COOH
Hydrochloric, nitric, and sulfuric acids are all strong acids as they
completely disparate into their ions
HCl➡️H*+Cl-
Carboxylic acids are weak acids as they
Only partially dislocate into their ions
Carboxylic Acids react in a similar way as strong acids with the four bases which are…
MAZIT metals
Metal Oxides
Metal Carbides
Alkalies (metal hydroxides)
Propanoic acid reacts with sodium hydroxide to form….
Sodium propionate
A salt
Name a salt of carboxylic acids thar are used as preservatives in the food industry
Calcium phosphate stops growth of mold
Alcohol +carboxylic acid 🔁??!
Ester +water
All esters contain an ester link, what is this?
O
⏸
➖C➖O➖
OR
➖COO
Describe esterification
(Making esters)
The carboxylic acid functional group condenses with the alcohol functional group to produce an ester link plus water
During esterification concentrated sulphuric acid is used to supply…
H+ ions
Concentrated sulfuric acid increases the…
Easter yeild by removing water…
According to le chatliers…
Esterification of ethanol with propanoic acid produces…
Ethyl propanoate
The first part of an esters name is from the …
Alcohol used
The second part of an esters name is from the …
Carboxylic acid
When making an easter why do we use a water bath
Alcohol and ester are flammable (Alternitive to bunsen burner)
When making an easter why do we use concentrated sulfuric acid
Provide H*(aq) ions
When making an ester why do we use a wet paper towel
Acts as a condenser
Stops alcohol and ester evaporating away
How do we know we have an ester
An immansible layer of ester
Distinctive smell
What is the purpose of NaHCO3 (aq) solution
To neutralise acid and any exess carboxylic acid
Esters prepared from alcohols and carboxylic acids with the same no. Of carbons have the same molecular mass and are therefore…
Isomers
Name some uses of esters
Flavouring
Perfumes
Adhesives
Medical applications
Hydrolysation of an ester produces…
The original alcohol and carboxylic acid
Hydrolysis
the break down pf large molecules into smaller molecules by the addition of water
Hydrolysing an ester using an acid
Requires the ester to be heated under reflux using dilute H* (aq) ions
What is the draw back of hydrolysing an ester using an acid?
The acid catalysed hydrolysis is reversible resulting in a mixture of alcohol/ carboxylic acid/ ester and water
Hydrolysis of an ester can be achieved by hydrolysing an ester using
a strong alkali.
To achieve complete hydrolysis of an ester the ester has to be added to..
A strong alkali and heated under reflux for approximately 30 minutes
Why is limonene insoluble in water
Its non polar so Its a hydrocarbon
Why is furanol soluble in water
All its functional groups are polar so it is soluble
Why is vanillin soluble in water
All its functional groups are polar
Why is eugenol insoluble
As an aromatic ring and a hydrocarbon chain exert a greater effect on solubility
Despite the polar functional groups
Properties of capsaicin
Insoluble in cold water
Responsible for the hot chili taste of jalapeños
Drinking water doesn’t take away the hot chilli effect but drinking milk does
Why is asparagus cooked in oil or butter
The flavour molecules in asparagus are water soluble so steaming or boiling it is not recommended as flavour would b lost
Why is broccoli boiled
The flavour molecules are soluble in oil so should be steamed or boiled to retain flavour
Vitamins
Can be water or oil soluble.
Fruits and veg containing vitamin C loose vitamin C when cooked in water
What is an example of oxidation
Burning alcohols in oxygen
Alcohols can undergo milder oxidation where the products depend on
Whether the alcohol is primary, secondary or Tertiary
Mild oxidation of alcohol can be achieved with
Acidified potassium Dichromate (orange ➡️ blue green)
Tollens regent (colourless ➡️ silver)
Black copper (II) oxide
(Black➡️ reddy brown)
Tertiary alcohols are not oxidised by mild oxidising agents
How does the ratio of hydrogen to oxygen indicate oxidation?
The oxygen ratio increases
Tetiary alcohols cannot be oxidised by mild oxidising agents as…
The carbon bonded to the -OH hydroxyl functional group is not bonded to a hydrogen atom
In a reaction of carbonyl compounds experiment what is the aim
To distinguish between the carbonyl compounds using benadicts solution, a mild oxidising agent
In a reaction of carbonyl compounds experiment what is the result
Only aldehyde is oxidised by benadicts solution (colour change blue ➡️ red orange) to form the equivalent carboxylic acid which turns universal indicator solution orange in colour
What is the formula for the colour change in benadicts solution
Cu^2*+2e-➡️Cu
Primary alcohols
Hydroxyl group is attached to carbon with two hydrogens
Oxidised by mild oxidising agents ( acidified potassium dichromate, tollens regent, copper(II) oxide) to and aldehyde
Secondary alcohols
Hydroxyl group is attached to carbon with one hydrogen
Oxidised by mild oxidising agents ( acidified potassium dichromate, tollens regent, copper(II) oxide) to ketone (a carboxyl compound)
Tertiary alcohols
Hydroxyl group is attached to carbon with no hydrogen
Not Oxidised by mild oxidising agents
Aldehyde
O
//
-C
\
H
Can be made into a carboxylic acid
O
//
-C
\
O-H
With benadicts solutionKetone
-C-
||
O
Carboxyl compound
Fats are…and oils are
Liquids
What are fats and oils made from
Glycerol and fatty acids
What is the chemical name and structure of glycerol?
H2c-o-H
|
H-o-cH
|
H2c-o-H
Propan-1,2,3-trol
Draw a fatty acid
O
//
~~~~~~C
\o-H
Describe fatty acids
Straight chained carboxylic acids that can be saturated or unsaturated and contain an even amount of carbons ranging from C14 to C24
Describe a fat or acid molecule
In fats and oils Esther links form between the -OH hydroxyl functional group and the -COOH carboxyl functional group and the fatty acids and a ratio of one glycerol molecule to three fatty acids
This molecule is known as a triglyceride molecule
Fatty acids used to make triglyceride can…
All be the same or two the same and one different all or three can be different
Fats are made from
Saturated fatty acid’s
The hydrocarbon tales of fatty acids in fats are held together by…
London dispersion forces of attraction
Why are fat solids
The saturated fat triglyceride molecules can pack more closely together then oil triglycerides
As a result the London dispersion forces of attraction between fat molecules are relatively strong so fat and relatively high melting points and are therefor solids at room temperature
Why are oils liquids
The shape of the unsaturated triglycerides oil molecule does not permit these molecules to pack closely
Consequently the London dispersion forces of attraction between the oil molecules is much lower than that of the fat molecules and they are therefore liquids
Low melting points of oils can be related to
Their are high degree of unsaturation ( c=c)
Due to c=c oils will quickly de colourise
Bromine water
How are vegetable oils hardened to make Margerine
Partial removal of unsaturation (C=C) by addition of hydrogen (hydrogenation) using a powdered nickle catalyst helps raise the melting point
After the Margerine is made what becomes of the nickel catalyst
It is removed (recycled)
Fats and oils are what in water?
Insoluble ie hydrophobic as they are non polar
Is vitamin A polar?
No
Is vitamin A polar?
Yes, subject to hydrogen bonding
Soaps are produced by…
The alkaline hydrolysis of fats and oils using sodium hydroxide (a strong alkali)
Producing the sodium salt of the fatty acid
Describe a soap molecule
Hydrocarbon tail is non polar and hydrophobic
Head is iconic and hydrophilic
How does soap clean
The nonpolar covalent hydrocarbon tail of the soap molecule bond to the non polar for greasy materials on fibres, skin or plates by London dispersion forces of attraction
That ionic head (-COO^-) of the soap molecule is attracted to the polar covalent water molecule by electrostatic forces of attraction
Grease mixing with soapy water is an example of…
Emulsion
What happens when soaps are used with hard water
Precipitate is formed instead of a soapy lather
This reduces the cleaning action of the sort and leaves a scum around the area of use
Describe hard water
Contains Mg2- and/or Ca2+
Describe the purpose of detergents and how they differ from soap
They have a soap like structure but do not form a precipitate when added to hard water
What is the purpose of lecithin, an example of its use and how this occurs
Mayonnaise is an emultion formed by mixing Olive Oil vinegar (mostly water) and egg yolk
Lecithin in egg yolk acts as an emulsifier helping the olive oil and water to mix
Lecithin is a monoglyceride molecule
Proteins are made of…
amino acids
Describe essential amino acid’s
Cannot be synthesised by individual organisms therefore they must be present in an individual’s diet
Describe the test for the presence of proteins using PHP paper
The protein plus soda lime is heated on a Bunsen burner in a test tube stopped with mineral wool
If amines or ammonia is present the paper will turn blue
Describe the test for the presence of proteins using Reflux
Proteins are hydrolysed using 50% HCL and reflux for several hours. The change from a cloudy suspension (protein) to a clear solution (of hydrolysed amino acids) indicates this insoluble protein has been hydrolysed into a soluble amino acid’s
How can you identify amino acids from hydrolysed proteins
Chromatography
Nitrogen compounds are converted into…
Amino acids
Amino acids contain the elements
Nitrogen, carbon, hydrogen and oxygen
What are the two functional groups of amino acids
Carboxyl groups
Amide group
Proteins are…
Condensation polymers made from amino acid monomers
Describe the hydrolysis of a protein
Breaks the C-N bond within the peptide link to produce an amide and a carboxylic acid
What kind of structure do fibrous (muscle and connective) proteins have
Long fibre like structures
If hydrogen bonding takes place between a peptide link of one fibrous protein and a peptide link of an adjacent fibrous protein….
A sheet like structure forms
Why are fibrous proteins tough and insoluble
The considerable extent of hydrogen bonding that binds the fibrous protein molecules strongly together
Give some examples of fibrous protein
Muscle, keratin in hair and nails, elastin in lungs and arteries
If hydrogen bonding occurs between peptide links within the same fibrous protein…
Spiral or helix structure is formed
Describe how a globular protein is formed
Within a helix the peptide links can hydrogen bond with other peptide links in the helix
Why are globular protein soluble
Some of their polar peptide links are on the outside of the molecule
What are the most common compounds found in essential oils
Terpenes
What are terpenes based on
The isoprene unit
What is the isoprene unit
2methylbuta-1,3-diene
C5H8
All terpenes contain…
Isoprene units joined together
Many terpenes found in nature have…
large molecules containing more than two isoprene units
How do you know how many isoprene units are in a terpene
Count the number of carbon atoms and divide by five
When terpenes are oxidised….
They form products that have different properties from the intended product and this alters their fragrance
In tea tree oil the terpene known as alpha terpene is oxidised to p-cymene and ascandol.
These oxidised products…
Cause allergic reaction when in contact with skin
Tea tree oil is sold in brown bottles and labled re seal after use with a sell by date, why?
To prevent photo oxidisation
Ultra-violet radiation
Has sufficient energy to break certain covalent bonds
Causes chemical reactions to occur in skin that make vitamin D
Can give us a sun-tan and age our skin through sun-burn that is linked to cancer
What describe the effect of sunscreen and sunblock
Prevents sunburn
By filtering (sunscreen) or blocking (sunblock) UV rays so that less reaches the skin
With sunblock containing titanium oxide that completely stops UV radiation
Free radical scavengers in sunscreen remove free radicals thus preventing chain reactions
Describe the role of vitamin C in food and drink
An anti-oxident, free radical scavenger that is added to food and drink to slow the rate of oxidation
Describe Free radical reactions in the context of Cl-Cl
Two chlorine atoms are bonded together by non-polar covalent bonds
When UV radiation is shone onto chlorine, the non-polar covalent bond is broken so forming two atoms
These are free radicals
Describe free radicals in the context of Cl-Cl bonds
Neutral and highly reactive as they have an unpaired election
Consider the reaction between Cl-Cl and H-H
It is a photochemical reaction
Cl2 and H2 react explosively when exposed to U.V radiation
What are the three stages in which the reaction occurs
Initiation
Propitiation
Termination
Consider the reaction between Cl-Cl and H-H
It is a photochemical reaction
Cl2 and H2 react explosively when exposed to U.V radiation
Describe the initiation stage
U.v. Radiation breaks the Cl-Cl non-polar covalent bond to form two chlorine free radicals
H-H non-polar covalent bond is much stronger so U.V radiation does not break it
Consider the reaction between Cl-Cl and H-H
It is a photochemical reaction
Cl2 and H2 react explosively when exposed to U.V radiation
Describe the propitiation stage
Highly reactive chlorine free radicals react with hydrogen
This produces a hydrogen free radical which reacts with a chlorine molecule producing a chlorine free radical and so on and so forth
Consider the reaction between Cl-Cl and H-H
It is a photochemical reaction
Cl2 and H2 react explosively when exposed to U.V radiation
Describe the termination stage
Free radicals can react with free radicals to form stable molecules
At any point two free radicals can collide and form a stable molecule
Free radicals are required for the reaction to continue but, once they have all reacted to form stable molecules then the reaction stops
Bromine water is quickly de colourised by the addition reaction with alkenes to form…
Bromoalkanes
Decolorisation of bromine water occurs more slowly with…
Alkanes
U.v radiation can cause free radicals to form in our skins that lead to…
Aging
How do cosmetic creams work?
They contain free radical scavengers that form stable compounds with the free radicals in our skin so limiting free radical chain reactions that cause skin to wrinkle
Describe how antioxidants work
An electron is transferred from the damaging free radical to the antioxidant which is converted into a stable free radical and the damaging free radical in neutralised
