Preparation of Ethanol and Ethanoic Acid
Length: 3009 words (8.6 double-spaced pages)
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Introduction to report
This report contains 5 practical experiments to produce ethanoic acid
from ethanol. The first practical is the preparation of ethanol from
glucose using yeast during the process of fermentation; this has been
demonstrated in class. In this practical the glucose is converted into
ethanol and carbon dioxide by respiratory enzymes from the yeast. The
ethanol solution will be between 5-15% and the ethanol will be
separated from the yeast by filtering. Then the ethanol will be
In the second experiment we are going to distillate ethanol solution,
which involve measuring both the volume and the mass of the ethanol
solution, we can work out the density from the volume and mass. We
will then compare the density of the solution with that of pure water
and pure ethanol; it is possible to calculate the percentage
concentration of the solution.
The third practical will be oxidising ethanol to ethanoic acid, in
this experiment we will start with 96% ethanol. We can achieve a
successful oxidation by boiling gently under reflux with acidified
The fourth practical is to distillate ethanoic acid solution; this is
the continuation of the third practical and involves distilling the
mixture to obtain a reasonably pure sample of ethanoic acid.
The final practical is the filtration of ethanoic acid solution; this
involves determining the actual % yield of ethanoic acid by titration
against 0.05 M sodium hydroxide.
Practical one Equation
yeast will carry out anaerobic respiration, using the glucose to
enable it to grow and multiply. The equation above shows what the
yeast will accomplish inside the bioreactor.
This equation also shows fermentation process, which proves an
anaerobic respiration, which means that oxygen is absent from the
process. Anaerobic respiration takes place in organisms and releases a
small amount of energy very quickly. In most organisms, it consists of
a chain of chemical reactions called glycolysis, which break down
glucose into pyrutic acid.
The following equations show how the yeast will turn the glucose into
pyruvic acid (carboxylic acid)
Practical three Equation
In this practical, ethanol will be oxidised with the assistance of
acidified sodium dichromate (VI)
The following equation shows what will happen:
Ethanol + oxygen ethanoic acid
(Alcohol) (Carboxylic acid)
What will happen, if micro- organisms are used as an alternative, will
be oxidised to ethanal and will be oxidised again to produce ethanoic
The difference between biotechnology and practical 3 is that
biotechnology uses the micro-organisms to produce a useful substance.
Practical 3 is just an oxidation process.
A further difference between biotechnology and practical 3 is that
biotechnology involves 2 stages, whereas, practical 3 requires only 1
stage before its process is complete. .The yeast carry out an alcohol
fermentation when grown anaerobically; in the presence of air, they
make carbon dioxide and water by aerobic respiration. Must look at
Isomers are molecules that have the same molecular formula, but have a
different arrangement of the atoms in space. That excludes any
different arrangements, which are simply due to the molecule rotating
as a whole, or rotating about particular bonds.
Where the atoms making up the various isomers are joined up in a
different order, this is known as structural isomerism. Structural
isomerism is not a form of stereoisomerism.
Structural isomerism is the relation of two or more compounds,
radicals, or ions that are composed of the same kinds and numbers of
atoms but differ from each other in structural arrangement (as CH3OCH3
and CH3CH2OH, or in the arrangement of their atoms in space and
therefore in one or more properties)
There are two types of isomerism one is structural isomerism; - where
the bonds between the atoms are arranged differently. And
Stereoisomerisms- where bonds are the same but the nature of bonds
allows a 3-D arrangement.
Structure/function of Starch & Cellulose Structure
Glucose is used to make cellulose and starch, because starch is a
polysaccharide and this is found in plants and also cellulose is
founded in the plants parts, and its polymer is b- glucose molecules
to form the long chains.
Starch & Cellulose Structure
Starch is a mixture of two-glucose polymers amylase and amyl pectin.
The ratio of these components varies from plant to plant. The usual
composition is 25% amylase but there are mutants with up to 50-70%,
and naturally occurring waxy starches, which are all amylopectin. The
amylase: amylopectin ration is an important determinant of starch
functionality. Cellulose is very similar to amylase in many ways. It
is a linear chain of 1,4 linked glucose molecules but the links are b
and the chain is often much larger. The b-1, 4 links causes the chains
to lie as flat ribbons rather than form helices. Cellulose chains can
pack parallel to each other in tightly hydrogen-bonded crystals. (In
fact, the large chains are hard to organize into crystalline layers
over their whole length and instead form alternate crystalline
amorphous and crystalline bands.)
Cellulose is a lot stronger than starch. Starch is practically useless
as a material, but cellulose is strong enough to make fibres from, and
hence rope, clothing, etc. Cellulose doesn't dissolve in water the way
starch will, and doesn't break down as easily. Breaking down or
dissolving in water just would be a little too inconvenient for
something we use to make clothes. Not to mention, a good soaking rain
would wash away all the wooden houses, park benches, and playground
equipment if cellulose were soluble in water.
Starch is a long (100's) polymer of Glucose molecules, where all the
sugars are oriented in the same direction. Starch is one of the
primary sources of calories for us humans being.
Cellulose is a long (100's) polymer of Glucose molecules. However the
orientation of the sugars is a little different. In Cellulose, every
other sugar molecule is "upside-down". This small difference in
structure makes a big difference in the way we use this molecule.
Difference between starch and cellulose
â€¢ Starch: 4 linkage, Spiral form; easy to hydrolyse; weak
â€¢ Cellulose: b-1, 4 linkages, Crystalline; hard to hydrolyse; strong
Ã˜ Optical isomerism is a form of stereo isomerism
Ã˜ The ring of carbon is basically flat with the OH and H groups either
above or below the plane of the ring.
Ã˜ The two forms of glucose are stereoisomers being mirror images of
each other they cannot be superimposed upon each other. (See diagram
Ã˜ In alpha glucose the OH group on Carbon 1, is below the plane of the
ring (see diagram 1 below); in beta glucose the OH group on Carbon 1
is above the plane (see diagram 2).
Ã˜ This type of isomerism is called optical isomerism because the two
isomers rotate plane-polarised light in different directions Light is
also made up of vibrations.
A substance that increases the rate of a chemical reaction, but is
chemically unchanged itself at the end of the reaction. This process
is known at catalysis. Catalysis works by lowering the activation
energy of a reaction. The catalyst used in a reaction is written over
the arrow in the equation. A catalyst, which increases the rate of one
reaction, may have no effect on another.
Catalysts increase the rates of reactions by providing a new mechanism
that has smaller activation energy, as shown in the diagram below. A
larger proportion of the collisions that occur between reactants now
have enough energy to overcome the activation energy for the reaction.
As a result, the rate of reaction increases.
Activation energy is the energy barrier that must be overcome during a
collision of two possible reactants in order for a reaction to occur.
Geometry is important since a head on collision would be different
from a collision from the side. It is found that collisions must have
a sufficient energy for a reaction to take place and this depends
exponentially on an energy factor called the activation energy.
Enzymes are globular proteins; their molecules are round in shape.
They have an area - usually of as a pocket-shaped gap in the molecule
- which is called the active site.
Some enzymes are found inside cells (intracellular enzymes), and some
- especially digestive enzymes - are released so they have their
effects outside the cell (extra cellular enzymes) .
Only the substrate or substrates fits into the active site. There are
several types of enzyme which contribute to different types of
biochemical reaction - see below. It is not widely appreciated that
water is also a reactant in the digestion (enzyme-controlled
breakdown) of most biological molecules.
The enzyme speeds up the process of conversion of substrates
(reactants) into products - usually so much that the reaction does not
take place in the absence of enzyme.
Although the enzyme obviously joins with the substrate for a short
while, the enzyme and substrate split apart afterwards, releasing the
enzyme. Thus the enzyme is not used up in the process unlike
substrates, so it can continue to react if more substrate is provided.
See the diagrams below on substrates and enzymes.
Within the normal range, changes in temperature of substrate and
enzyme affect the rate of reaction in accordance with predictable
relations between enzyme and substrate molecules.
The effects of temperature may be explained on the basis of kinetic
theory - increased temperature increases the speed of molecular
movement and thus the chances of molecular collisions. Enzymes have an
optimum temperature for their action.
Above normal temperatures say 60 Â°C, heat alters permanently the
enzyme molecule. This denature is caused by heat. This change -
especially in the region of the active site - mean that the enzyme is
inactivated, even when returned to normal temperature.
It would be wrong to say that an enzyme is KILLED by heat, since it is
only a molecule, not an organism.
The higher the temperature to which the enzyme is given and the longer
the heating is continued, the more it becomes denatured and becomes
Below normal temperatures, enzymes become less active, due to
reductions in speed of molecular movement, but this is reversible, so
enzymes work effectively when returned to normal temperature.
The lock and key theory
The lock and key theory is simply a way of describing how specific an
enzyme is for its substrate. Just like a lock requires a specifically
shaped key for it to work so does an enzyme. Each enzyme is a protein
which is a polypeptide chain folded into a complex 3 dimensional
structure. Part of that structure contains the active site, which is
where the enzyme can bind to the substrate on which it will perform
some chemical reaction. Because each enzyme performs a specific task
on a specific substrate the active centre of the enzyme can be
considered to be the "lock" which requires the specific "key" or
substrate to perform the function. (see below for diagram on the key
and lock analogy)
How the theory can be explain and how this works?
* Lock and Key analogy is the best way to explain this theory or
* Smaller keys, larger keys, or incorrectly positioned teeth on keys
(incorrectly shaped or sized substrate molecules) do not fit into
the lock (enzyme). Only the correctly shaped key opens a
particular lock. The characteristics of the puzzle pieces are
specific, not all fit, some look similar. Enzymes are like this -
hence the lock and key see next page for diagram.
* Some pieces look the same or look similar but only specific
actually go together. Analogy - puzzle pieces fitting together
* There is a specific site that it fits
* A fits B, but not C, even if B and C are similar
Enzymes: Structure/shape and Function
Cells perform their functions (growth, reproduction, specific
metabolic activities, etc.) by using various types of chemical
reactions. These reactions must be carried out in an orderly fashion
(when to begin, when to stop, rate of reaction, etc.) for a cell to
function efficiently. To perform these orderly processes cells
regulate chemical reactions through the use of enzymes. Enzymes are
biological (protein) catalysts. Enzymes couple reactants together to
form products, driving energy requiring endergonic reactions with the
energy release by exeronic reactions. The three-dimensional shape of
the enzyme in the diagram below shows how the substrate entering the
enzyme. The shape and the structure of the enzyme allow the substrate
easily to enter.
Introduction (Section4) banner
Biotechnology can be defined as "using living organisms or their
products for money-making purposes." As such, biotechnology has been
practiced by human society since the beginning of recorded history in
such activities as baking bread, brewing alcoholic beverages, or
breeding food crops or domestic animals. A narrower and more specific
definition of biotechnology is "the commercial application of living
organisms or their products, which involves the deliberate
manipulation of their DNA molecules". This definition implies a set of
laboratory techniques developed within the last 20 years that have
been responsible for the tremendous scientific and commercial interest
Biotechnology is used to Modify Plants and Animals by combining DNA
from different existing organisms (plants, animals, insects, bacteria,
etc.) results in modified organisms with a combination of traits from
the parents. The sharing of DNA information takes place naturally
through sexual reproduction and has been exploited in plant and animal
breeding programs for many years. However, sexual reproduction can
occur only between individuals of the same species. A Holstein cow can
be mated with a Hereford bull because the two animals are different
breeds of the same species, cattle. But trying to mate a cow with a
horse, a different species of animal, would not be successful.
Differentiates between Traditional and modern biotechnology
Traditional biotechnology refers to a number of ancient ways of using
living organisms to make new products or modify existing ones. In its
broadest definition, traditional biotechnology can be traced back to
human's transition from hunter-gatherer to farmer. As farmers, humans
collected wild plants and cultivated them and the best yielding
strains were selected for growing the following seasons.
With the domestication of animals, farmers applied the same breeding
techniques to obtain desired traits among animals over generations.
In modern biotechnology, achieving desired individuality in an
organism is done mostly at the gene level. Hence the gene responsible
for the desired trait is identified, transferred and inserted into the
organism at the cell level, to produce genetic changes. Also in other
modern techniques of biotechnology such as mutagenesis, past knowledge
of causes of mutations, known as mutagens, (such as exposure to
radiation or temperature extremes) has been harnessed to generate
intentional changes in the genetic make-up of a cell or plant tissue.
For example, mutation breeding is a biotechnology technique commonly
used to develop plants with novel traits. In mutation breeding, plant
tissues are exposed to powerful mutagens in hopes of causing
beneficial changes in the genetic make-up of the plant cells and then
exposed to the conditions under which the plants would have to grow
(such as pesticides, limited amounts of water and so forth). Those
plants which, experienced beneficial mutations survive the exposure to
the conditions and are bred and developed into plant lines.
Enzyme technology is associated with the use of enzymes as the tools
of industry, agriculture and medicine. The majority of enzymes used in
industrial or biotechnological applications are derived from
particular fungi (Aspergillus) and bacteria. Safe organisms must be
used for consumer-related uses.
Food in let
Harvesting tube -syringe
In the solution of bioreactor, will contain yeast Using baker's yeast
(Saccharomyces cerevisiae) glucose
The bio-reactor was correctly set up ready to use by the technician.
This practical did not involve any work since it was a class demo. The
bio-reactor was let to work for a week with the solution which
contained glucose and yeast. After the week the solution was ready to
Inside the bioreactor the micro-organisms grown in the liquid of the
glucose and their growth level can be measured, there is four phases
of growth occurs in the micro-organisms.
The first is the lag phase where small growth occurs because the
micro-organisms are getting used to their new surrounding. The second
is exponential phase this is when the number of micro-organisms is
multiply by 2 between 20-30 minutes. Then thirdly it goes into
stationary phase, at this stage growth slows down and stops because of
the fact that there might be a lack of food or build up of toxic
waste. Lastly it goes into senescent phase at this stage the
micro-organisms are vanishing because of the same reason in the
stationary phase: lack of food or build up of waste. Since batch
culture was used for practical 1, this means that fermentation is set
up and left run for a week without adding anything to the solution.
Practical 2: Distillation of the ethanol solution
We took fermentation product from bioreactor and set up for
distillation. The amount we used was 20 cm3 of fermentation product
and was weighed on a digital weighing scale inside a 250ml beaker, we
had to weigh the beaker first because we only wanted the weight of
solution not the beaker and then subtracted the weight of beaker from
the solution to get solution weight by it self, which was 18.7g of the
distillate product of ethanol, but our solution was spilt a little
showing that this error could effect practical a slightly.. And
afterward the weight of solution was recorded.
Distillation was set as in the diagram below:
After the distillation we collected 4.6g of distilled product
We worked out the percentage yield to be:
% yield = actual yield x 100
% yield = 4.60 x 100 = 24.6%
Practical 3: Oxidation of ethanol to ethanoic acid
We poured into a pear-shaped flask 10 cm3 of 1 M sulphuric acid. After
added 5g sodium dichromate (VI) using a funnel, and 3 drops of
anti-bumping granules. We swirled the flask gently until all the
sodium dichromate was dissolved. We then very slowly of a lot of care
added 2 cm3 of concentrated sulphuric acid with a funnel opening the
tap gently drop by drop. The flask with solution was cooled under a
cold tap water this is because the sulphuric acid we added earlier on
made the solution gain heat. Now we were ready to set up for reflux,
the apparatus was set up as shown below.
1 cm3 of ethanol (CH3COOH) was added down the condenser, once again
very gently drop by drop. The ethanol solution was then boiled for 20
minutes under reflux. We could now work out the mass but we don't know
the density so we have to rearrange the formula: Density = mass, we
rearrange to get Mass= density x volume volume
Practical 4: Distillation of the ethanoic acid solution
This practical was the continuation of practical 3 in the previous
page, and involved distilling the mixture to obtain a reasonably pure
sample of ethanoic acid.
In this section evaluate data; in particular consider its reliability.
Must include the following to achieve the criteria:
Â· Comparison of results with published data (c3)
Â· Discussion of the accuracy and reliability of the various methods
used for checking purity; do this by considering errors and comparing
the results with partner and with the published data (A2)
Â· Discussion of the accuracy of the percentage yield determination
Comparison with industrial processes
Romford Brewery is a very large company with 600 personal; they make
250 million pounds from beer each year. They replaced their old manual
system by a high tech computerised automation system. The automation
made the production of beer very easy and quicker because the
computers controlled everything that would normally done by hand, like
the mashing process is monitored by computer which controls the
temperature; the adding of the hobs which once again are computer
controlled so that the beer has the right bitter favour and checked
the temperature was right before adding of the hobs; the fermentation
process is Romford produces 750 thousand barrels of beer a year, a
barrel is equivalent 288 pints, and works out 1250 barrels per
employee. All the beer made is supplied to 100s of pubs.
Advantages of automation
Â· Made the process more efficient.
Â· Saved more money and time in the long run.
Â· Reduced labours costs by employing less personal.
Â· Allows them to produce economy of scale: a continuous. process same
as mass production which is cheaper than batch production that Ridley
Â· Heat exchanges save them money because the heat produce from
fermentation can be used for another process.
Disadvantages of automation
Â· The automation cost 13 Â½ million
Â· Romford has to still employ a lot of personal
Â· The system will consume large a amount electricity
Comparison of practical one with brewing
The starting material