Assignment 18 March 2015

In Canada, major sources of SOx mostly come from non-ferrous smelters, then coal-fired generators. Major source of NOx is motor vehicles. Half of East Canada’s wet sulphate deposition come from US whereas 10% of wet sulphate deposition in North-Eastern US come from Canada. Acid rain has affected Canada’s ecology and water quality.

In the UK, the country is a considerable emitter of acidic pollution compared to other countries. Most UK SO2 come from power stations and other industries whereas the largest source of NOx is road transport.

In Europe, during the 1970s and 1980s, with the use of tall chimneys in industry and power generation increasing, acid deposition became a particularly prevalent problem. It is found that the amounts of SO2 and NO being emitted are different from acidic pollution deposited. Some countries were emitting small quantities of pollutants yet deposition was observed to be several times greater.

Implications of Stereoisomerism in Drugs to Society


Stereochemistry may seem like a trivial subject because there are no major differences between stereoisomers. In nature however, especially in the biological system like a human body, these minor changes may have severe consequences.


In society, many drugs are composed of a single stereoisomer of a compound, and while one stereoisomer may have positive effects on the body, another stereoisomer may be toxic. Due to this, one of the key roles of organic chemists consists of synthesizing compounds consisting of a single stereoisomer.

In some instances, toxicity has been linked to one member of a pair of isomers. This pair need not be the active isomer for the substance to be toxic. For example, granulocytopenia is related to the d-isomer of levodopa and vomiting is caused by the d-isomer of levamisole.

Shown below is another example – the binding of Ibuprofen, a common pain reliever. While one stereoisomer of the compound has the right three-dimensional shape to bind to the protein receptor, the other does not and can not bind, and is therefore ineffective as a pain reliever.


One of the most common examples of the impact of stereochemistry cites back to the thalidomide disaster. Thalidomide is a pharmaceutical drug, first prepared in 1957 in Germany, prescribed for treating morning sickness in pregnant women. The drug was discovered to be teratogenic (able to disturb the growth and development of an embryo or fetus), causing serious genetic damage to early embryonic growth and development, leading to limb deformities in babies. In the human body however, thalidomide undergoes racemization: even if only one of the two enantiomers is administered as a drug, the other enantiomer is produced as a result of metabolism. Thus, it would be incorrect to state that one of the stereoisomer is safe while the other is teratogenic. Thalidomide is currently used for the treatment of other diseases, notably cancer and leprosy. Strict regulations and controls have been enabled to avoid its use by pregnant women and prevent developmental deformations. This disaster was a driving force behind requiring strict testing of drugs before making them available to the public.

Therefore, the importance of stereochemistry in biological systems extends to more than just drugs and medicines. The human body, for example, can only create and digest carbohydrates and amino acids of a certain stereochemistry. Thus, all of our proteins that make up our hair, skin, organs, brain, and tissues, are composed of a single stereoisomer of amino acids. Moreover, our bodies can make and digest starch (found in potatoes and bread) but not cellulose (found in wood and plant fibers), even though both are just polymers of glucose of different stereochemistry.


The Chemical Concept of Stereoisomers


Isomerism in a chemical compound is the existence of different arrangements of atoms with the same chemical formula. There are 2 kinds of isomerism:

Structural Isomerism, where isomers of different structures arise from

  • Different position of carbon chains
  • Different position of functional groups
  • Different functional groups

Stereoisomerism, where isomers have the same structure and sequence of atoms, but different spatial arrangement. There are 2 kinds of stereoisomers:

  • Geometric isomers are centered about a C=C bond. These are also known as cis-trans isomers
  • Optical Isomers are centered about chiral carbon.

Our team will focus on stereoisomerism(in particular, optical isomerism) and how it can change the effects of drugs.


A chiral molecule is centered about a chiral carbon that has 4 different functional groups attached to it and cannot be superimposed with its mirror image. The concept is similar to how our left and right hands are mirror images of each other but not superimposable. Two mirror images of such a molecule are known as enantiomers, and a mixture containing equal amounts of both enantiomers is known as a racemic mixture.

Enantiomers are often named by R/S system. To name enantiomers by the R/S system, the viewer needs to orientate the molecule such that the functional group with the lowest priority, according to the Cahn–Ingold–Prelog priority rules, is pointed away from the viewer. The R-enantiomer is the one with the priority of the remaining 3 functional groups decrease in a clockwise direction and the S-enantiomer is the one that decreases in an anti-clockwise direction.

The +/- system of naming is also often used, in reference to the direction in which the enantiomers rotate polarised light.

To appreciate how stereoisomerism affects drugs, we have to first consider that biological molecules often react with each other via the “lock-and-key” mechanism. As a result, if a molecule is able to fit another reactant molecule, its enantiomer may not due to a different 3-D spatial arrangement. This will lead to the enantiomer being an inactive compound or a compound that reacts differently.


Stereochemistry in Drug Action, Jonathan McConathy, Ph.D. and Michael J. Owens, Ph.D. Link:

Unit 8 Lecture Slides 48-49.

Meeting Minutes 15 Mar 2015

Virtual Location: Google Docs 

Time and duration: 4pm, 2 hours

Team members who attended and members who missed the meeting with clarification on their reasons for missing it.


Andrew Fung


Andrew Teng

Andreas dwi putra

Ardyanto widjojo

Anshuman subsequently followed up with tasks from 6-7pm

Topics discussed (briefly)

Chemical Concept

-Focus on optical isomers

Implications on Society

-Find examples of enantiomers in drugs that have different effects on the human body

Tasks to be done before the next meeting and who has been assigned/agreed on doing them.

Brainstorm on video

Problems arising if any


Plan of action

Chemical Concept and Implications to Society to be filled.

Meeting was adjourned.

First Assignment on Unit 3

Q1) Understanding Earth’s energy balance is essential to understanding the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter, but the energy leaving Earth’s surface averages 390 watts per square meter. Why isn’t Earth cooling rapidly?


When the earth was formed, the particles that accreted actually had some energy so when they got together that energy was imparted into the Earth and it had some embodied energy to start with.


Another reason is due to gravity. Because gravity works through an object’s centre of mass, heavier objects are pulled towards the centre of the Earth and lighter objects are therefore displaced above them towards the surface, and that would have generated some frictional effects. Therefore some gravitational potential energy was converted into heat. However,  these two mechanisms are quite minor contributions. The biggest mechanism is what we call radiogenic heating.


The Earth is a giant nuclear reactor.  There are particles in the Earth’s core and throughout the mantle which are radioactive.  When things decay radioactively they produce heat.  The vast majority of the Earth’s energy is coming from the radioactive decay of these components, and they include things like thorium and also potassium. Therefore the earth is not actually cooling down, as geological estimates are that the Earth loses heat at a rate of about 50 terawatts.  That’s about 50,000 1 gigawatt power stations worth of heat loss, i.e. if power stations pump out power at a rate of 1 gigawatt then you’d need about 50,000 of them – that’s how fast the Earth is losing heat through the oceans, continental surfaces, volcanoes and so on, and that means that those processes inside the Earth must be producing heat energy at a similar rate to balance things out because the Earth isn’t cooling down that much.


Q2) Do you think the statement made by the cartoon is justified? Explain.


No. A warming climate might affect snowfall. There are two competing effects as the climate warms: the increasing temperature causes a changeover from snow to rain, but it also increases the amount of water vapor in the atmosphere. For a particular place and time of year, which effect wins out depends on the temperature to begin with.

For relatively mild regions, we would expect heavy snowfall to become increasingly rare as the climate warms. But in colder regions, heavy snowfalls can become more frequent because of increases in the amount of water vapor in the atmosphere or, in some cases, because of changes in the circulation of the atmosphere, such as a shift in position of the storm track.

Extremely heavy snowfall requires a combination of an intense storm and the right temperatures. If it’s too warm, then most of the precipitation falls as rain. If it’s too cold, then there isn’t enough water vapor to give a big snowfall. All else being equal, there is a sweet spot in a fairly narrow temperature range around 24 degrees Fahrenheit.


Q3) One of the first radar devices developed during World War II used microwave radiation of a specific range that triggers the rotation of water molecules.Why was the design not successful?


The design was not successful as there exist water molecules in the atmosphere which are able to absorb the radiation, interfering the detection of intended objects.

Q4) Now that you have studied air quality (Unit 1), stratospheric ozone depletion (Unit 2) and global warming (Unit 3), which do you believe poses the most serious problem for you in the short run? In the long run?


In the short run, air quality has the most severe impact on mankind because of its direct impact on health. Poor air quality can cause respiratory problems in humans when inhaled and its health effects surface within a short time span.


Global warming and ozone depletion pose a more serious threat in the long run, however, because their impact on human lives are indirect. Global warming causes melting glaciers resulting in rising sea levels that may submerge low-lying lands and ozone depletion allows the penetration of harmful UV-C radiation through the stratosphere in the Antarctica region. Due to the absence of human population in the Antarctica, the effects of UV-C radiation does not directly impact mankind. Thus global warming and ozone depletion are less of a threat in the short run compared to air quality.


In the long run, global warming would pose a more serious threat as entire low-lying civilisations would be submerged. On the other hand, the effects of cancer due UV-C radiation only surfaces after prolonged exposure and would take an extended period of time for the severity of its effects to be apparent.

Introduction and Our Team

Introduction of Our Topic

Our team has chosen to focus on the stereochemistry of isomers and how subtle differences in structures can affect the effects of a certain drug. We feel that this topic is important and relevant as it focuses on the spatial arrangement of atoms to form molecules and gives us the opportunity to study the effects different arrangements have on these molecules.


Team Members’ Self-Introduction

Andreas Dwi Putra – Year 2 Material Science Engineering student! I am from Indonesia. My hobby are playing computer games and watching football.

Anshuman Anand – Year 2 Mechanical Engineering student! I am an expat living in Singapore for the last seven years. My interests include playing and watching football, and other adventure sports like go-karting and jet skiing.

Jaslyn – Year 2 chemistry student who can write mirror imaged words! Ever read the book Da Vinci Code?

Ardyanto Widjojo – Year 2 Mechanical Engineering  student!

Andrew Teng – Year 2 chemistry student, enjoys eating.

Andrew Fung – Year 1 Mechanical Engineering student who can enjoys playing the violin.


Meeting Minutes 16 Feb 2015

Virtual Location: Google Docs 

Time and duration: 9pm, 2 hours

Team members who attended and members who missed the meeting with clarification on their reasons for missing it.


Andrew Teng



Andreas Dwi Putra

Ardyanto Widjojo

Did not attend:

Andrew Fung absent for band rehearsal.

Topics discussed (briefly)

Assignment questions

Blog set up

Tasks to be done before the next meeting and who has been assigned/agreed on doing them.


Problems arising if any

Failure to find link to blog. Subsequently resolved by Andrew Fung.

Plan of action

Assignment to be uploaded.

Meeting was adjourned.