CM8001 Group 36

Unit 9- Molecules and Drugs

Question 1

In allergy sufferers, histamine causes runny noses, red eyes, and other symptoms. Here is its structural formula.

a. Give the chemical formula for this compound.

C5H9N3

b. Circle the amine functional groups in histamine

(circled in picture above)

c. Which part (or parts) of the molecule make the compound water-soluble.

The amine groups.

 

Question 2

Antihistamines are widely used drugs for treating symptoms of allergies caused by reactions to histamine compounds. This class of drug competes with histamine, occupying receptor sites on cells normally occupied by histamine. Here is the structure for a particular antihistamine.

a. Give the chemical formula for this compound.

C16H21N3

b. What similarities do you see between this structure and that of histamine (shown in the previous question 1) that would allow the antihistamine to compete with histamine?

Like histamine, antihistamine has ringed structures, the terminal N group of histamine is also similar to the amine group of histamine, moreover, in both molecules, the two aforementioned groups are connected by a spacer (akyl chain). These similarities allow antihistamine to compete with histamine and therefore inhibit histamine competitively.

Question 3

Consider this statement. “Drugs can be broadly classed into two groups: those that produce a physiological response in the body and those that inhibit the growth of substances that cause infections.” Into which class does each of these drugs fall?

a.Aspirin, b.Morphine, c.(Keflex) antibiotic, d.Estrogen, e.Amphetamine, f.Penicillin

Produce a physiological response in the body: aspirin, morphine, estrogen, amphetamine (a, b, d, e)

Inhibit the growth of substances that cause infections: (Keflex) antibiotic, penicillin (c, f)

Question 4

Herbal or alternative medicines are not regulated in the same way as prescription or OTC medicines. In particular, the issues of concern are identification and quantification of the active ingredient, quality control in manufacture, and side effects when the herbal remedy is used in conjunction with another alternative or prescription medicine.

a. What do you think is the evidence from herbal supplement manufacturers that address these issues?

Manufacturers usually address these issues by printing a disclaimer/warning on the box/packaging that informs consumers of possible consequences of consuming the product in conjunction with other forms of medication/supplements. This is usually followed by a line advising consumers not to do so.

b. Do you know anything about Singapore’s legislation on the topic?

Traditional medicines that are not in finished dosage forms such as pills or tablets are not subject to pre-market approval and licensing for their import and sale.

However, the salesperson must ensure that the medicine does not contain any prohibited substances.

 

Unit 8- The World of Polymers and Plastics

Question 1

When Styrofoam packing peanuts are immersed in acetone (the primary component in some nail-polish removers), they dissolve. If the acetone is allowed to evaporate, a solid remains. The solid still consists of Styrofoam, but now it is solid and much denser. Explain. Hint: Remember that Styrofoam is made with foaming agents.

Although it looks like a chemical reaction due to the large change in size, it is actually a physical reaction of dissolving. The acetone (the solvent) in the nail polish will cause the styrene (the solute) to dissolve. The large change in size is because styrofoam consists largely of air, thus, as the air escapes, only the small amounts of styrene dissolved in acetone are left. When the acetone evaporates, solid styrene is left.

This styrene could have air introduced into it again and become styrofoam afterwards.

Question 2

Consider Spectra, Allied-Signal Corporation’s HDPE fiber, used as liners for surgical gloves. Although the Spectra liner has a very high resistance to being cut, the polymer allows a surgeon to maintain a delicate sense of touch. The interesting thing is that Spectra is linear HDPE, which is usually associated with being rigid and not very flexible.

a. Suggest a reason why branched LDPE cannot be used in this application.

LDPE is not strong enough to have a very high resistance to being cut.

b. Offer a molecular level reason for why linear HDPE is successful in this application.

Linear HDPE chains are arranged in a way that they are strong enough for this application. Using a thin layer of HDPE will enable it to be more flexible.

Question 3

When you try to stretch a piece of plastic bag, the length of the piece of plastic being pulled increases dramatically and the thickness decreases. Does the same thing happen when you pull on a piece of paper? Why or why not? Explain on a molecular level.

Plastic is a series of long chain polymers. When the piece of plastic is stretched, the molecules are aligned parallel to each other and facing in the direction of the pull. However, when the same pulling force is applied to a piece of paper, the paper tears rather than stretching as the cellulose molecules in paper are held far more rigidly in place, and are not free to become aligned. They are similar to the cross linked polymers and does not stretch.

Question 4

A Teflon ear bone, fallopian tube, or heart valve? A Gore-Tex implant for the face or to repair a hernia? Some polymers are biocompatible and now used to replace or repair body parts.

a. List four properties that would be desirable for polymers used within the human body

It should be non cytotoxic, stable for a long time of extended use, has low reactivity with body fluids and acceptable elasticity.

b. Other polymers may be used outside your body, but in close contact with it. For example, no surgeon is needed for you to use your contact lenses-you insert, remove, clean and store them yourself. From which polymers are contact lenses made? What properties are desirable in these materials? Either a call to an optometrist or a search on the Web may provide some answers.

Contact lenses are made from hydrogel, it absorbs water so as to transmit oxygen into eyes.

The contact lens is a device that covers part of the cornea, for such a device, it would be desirable if the material used allows oxygen to pass so that extended wearing will not harm the cornea while being able to absorb water ensures hydration of the covered portion of the cornea to a certain degree, increasing the comfort while wearing the lenses.

c. What is the difference in the material used in “hard” and “soft” contact lenses? How do the differences in properties affect the ease of wearing of contact lenses.

Hard contact lenses were made of a type of plastic called poly methyl methacrylate (PMMA).

Since oxygen cannot pass through a PMMA contact lens, the only way for this vital element to reach the cornea was for tears to wash underneath the lens with each blink. In order for this blink-induced, tear-pumping action to occur, PMMA lenses had to be made relatively small in size. Also, there had to be a significant gap between the edge of the lens and the surface of the cornea.

These design characteristics made many people very aware of PMMA lenses on their eyes or caused discomfort that made wearing the lenses impossible. In some cases, these features also caused problems with PMMA lenses popping off the eye, especially during sports.

Most GP (soft) lenses incorporate silicone, which makes them more flexible than PMMA, thus the permeability-related design constraints that plague the hard lenses are largely overcome, allowing the soft lenses to actually be designed with comfort in mind.

Source: http://www.allaboutvision.com/contacts/rgps.htm 

Unit 6- Neutralising the Threat of Acid Rain

Question 1

Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in the Ohio Valley. Noting this, the National Parks Conservation Association (NPCA) reported that this national park had the poorest visibility of any in the country.

a. What is the connection between coal-fired plants and poor visibility?

Coal contains varying amounts of sulfur, hence coal-fired plants will release SO2 gas as burning of sulfur in oxygen produces SO2 gas which is poisonous.

S(s) + O2(g) -> SO2(g)

Once in the air, the SO2 can react with oxygen molecules to form sulfur trioxide.

2 SO2(g) + O2(g) -> 2 SO3(g)

SO3 then reacts with water to form sulfuric acid.

SO3(g) + H2O(l) -> H2SO4(aq)

Poor visibility, which is haze, results from tiny droplets of liquid or solid particles suspended in air. Many molecules of sulfuric acid form tiny droplets. These droplets form aerosols that do not absorb sunlight but reflect it thus reducing visibility.

b.The NPCA reported “the average rainfall in the Mammoth Cave National Park is 10 times more acidic than natural.” From this information and that in your text, estimate the pH of rainfall in the park.

pH 4

Question 2

Here are examples of what an individual might do to reduce acid rain. For each, explain the connection to producing acid rain.

a. Hang your laundry to dry it.

Requires less energy compared to using a clothes dryer, hence reduces the need for power plants to produce electricity by burning coal.

b. Walk, bike, or take public transportation to work.

Reduces gasoline used, cuts down on NOx emissions and thus reduces acidity of rain.

c. Avoid running dishwashers and washing machines with small loads.

Consume less electricity and reduces the burning of coal by power plants.

d. Add additional insulation on hot water heaters and pipes.

Reduces heat loss, thus less electricity needed to heat up the hot water, and less need for power plants to burn coal.

e. Buy locally grown produce and locally produced food

Reduces NOx emissions from vehicles (e.g. planes, ship) that bring in imported food, thus reducing acidity of rain.

Question 3

a. Give names and chemical formals for five acids and five bases.

Acids:

1. Nitric acid HNO3
2. Sulfuric acid H2SO4
3. Hydrochloric acid HCl
4. Carbonic acid H2CO3
5. Hydrofluoric acid HF

Bases:

1. Sodium hydroxide NaOH
2. Ammonium hydroxide NH4OH
3. Barium hydroxide Ba(OH)2
4. Calcium hydroxide Ca(OH)2
5. Lithium hydroxide LiOH

b. Name three observable properties generally associated with acids and bases.

Acids:

1. Turn blue litmus paper red
2. React with reactive metals to produce hydrogen gas
3. Sour taste

Bases:

1. Turn red litmus paper blue
2. Slippery feel when dissolved in water
3. Bitter taste

Question 4

The concerns of acid rain vary across the globe. Many countries in North America and Europe have websites dealing with acid rain. Either search to locate one (“Canada, acid rain”) or use these links to websites in Canada, the UK, or Europe. What are the issues in Singapore? Does the acid deposition originate outside or inside the Singapore’s borders?

URLs:

http://www.ec.gc.ca/

http://www.ukawmn.ucl.ac.uk/

http://www.grida.no/

http://www.nea.com.sg/

Acid rain could cause Singapore’s remaining native species to become extinct at Singapore’s Bukit Timah Nature Reserve (Straits Times  ‘Native species may be wiped out by acid rain’ Sept 14 2009). However, NParks replied that the acidity of the streams may not be caused by acid rain as the streams could be naturally acidic, thus a conclusion cannot be made until more studies are done. 

Acid deposition could originate inside Singapore’s borders as there are many local emitters of sulfur dioxide such as motor vehicles, refineries, power stations, shipping and other industries, according to NEA. Sulfur dioxide and NOx emission contribute to acid rain.

Source: http://wildsingaporenews.blogspot.sg/2009/09/native-species-in-singapore-may-be.html#.WMo92Pl97ic

http://www.straitstimes.com/singapore/pushing-for-higher-air-quality

Unit 5- Water for Life

Question 1

How can you purify your water when you are hiking? Name two or three possibilities. Compare these methods in terms of cost and effectiveness. Are any of these methods similar to those used to purify municipal water supplies? Explain.

Boiling water before drinking is one of the most reliable ways to purify drinking water. The basic rule is to make sure you bring the water to a rolling boil for 1 minute at lower altitudes and 3 minutes at altitudes above 2000 meters. Boiling will eliminate bacteria, protozoa, and even viruses. The downside is you’ll use up your cooking fuel and will need to wait for the water to cool down.

Chemical purification methods weigh almost nothing and are small enough to keep in your first-aid kit so you always have a way to purify water on the trail. Traditionally hikers used iodine tablets, but iodine wasn’t able to eliminate Cryptosporidium and also left the water yellow and tasting weird. Today hikers prefer Chlorine Dioxide Tablets, which purify water with a highly active form of oxygen as they dissolve. The downside is needing to wait 30 minutes for the tablets to effectively neutralize Giardia and up to 4 hours when Cryptosporidium is a concern.

Ultraviolet purifiers neutralize bacteria, protozoa, and viruses with UV rays. Fill a 32 ounce Nalgene water bottle and stir with the ultraviolet purifier for 90 seconds to have purified water. A prefilter is used for murky water and extra batteries should be carried.

Boiling is said to be the convenient and effective method while ultraviolet purifiers is the most costly method.

Chemical purification would be similar to how we purify our water in Singapore, using disinfectants like the chlorine tablets such as using ozone or chlorine to get rid of bacteria and viruses.

Source: https://www.outsideonline.com/2011516/top-5-water-filtration-systems-market

 

Question 2

Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

The two most common desalination techniques are distillation and reverse osmosis. Both of these require energy to remove salts from seawater or brackish water, and thus inherently are expensive. If a less expensive option is available (such as hauling fresh water from a distance), then the less expensive option is used.

Furthermore, it contributes to greenhouse gases as the process of removing salt from water is consequential to the environment and results in air pollution.

Question 3

Water quality in a chemical engineering building on campus was continuously monitored because testing indicated water from drinking fountains in the building had dissolved lead levels above those established by NEA.

a. What is the likely major source of the lead in the drinking water?

The likely source of lead is from solder in the pipe joints or from lead pipes themselves.

b. Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.

Research activities should not contribute to lead in the drinking water, assuming that any lead compounds are disposed of using prescribed methods. Although many undergraduate chemistry experiments used to use lead, most now have been redesigned to avoid it and other toxic metal ions completely.

Question 4

Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar compounds? Explain.

Only water-soluble vitamins are polar compounds, while fat-soluble vitamins are mostly non-polar compounds. Fat-soluble vitamins are mostly non-polar due to the fatty acid chains and they only have a small polar region. Polar water-soluble vitamins form hydrogen bonds with water molecules and thus can dissolve in water, while fat soluble vitamins do not.