Organic Chemistry Part 2
Benzene Benzene is a special structure C 6 H 6 The carbon-carbon bonds aren t a single or double bond but something in-between Resonance bond
CYCLIC HYDROCARBONS Carbon chains sometimes form ringed or cyclic structures
There are many compounds that contain benzene rings
2,4,6-trinitrotoluene
BENZENE HEALTH RISKS Acute Neurological symptoms: dizziness, drowsiness, headaches, and loss of consciousness, reddening and blistering, irritation to the eyes, skin, and can also result in respiratory problems Larger doses: vomiting, dizziness, and convulsions, and death Chronic Longer term exposure an affect the tissue that is responsible for producing blood cells excessive bleeding, immune system deficiencies, and anemia Chromosomal problems can occur on a structural or numerical level. Cancerous effects Benzene has been classed as a group A carcinogenic by the Environmental Protection Agency Greater risk of leukemia Other effects Females suffer a decrease in the size of the ovaries as well as menstrual problems In animal tests, pregnant animals that were exposed to benzene though inhalation sustained fetus damage, including effects such as low birth weight, bone marrow problems, and problems with bone formation.
Charbroiling your meat cause the formation of POLYCYCLIC AROMATIC HYDROCARBONS (PAHs))
Benzene (and other VOCs) present in gasoline can enter the water table and contaminate drinking water.
Many benzene-containing molecules are considered to be PERSISTENT ORGANIC POLLUTANTS (POPs) POPs undergo BIOLOGICAL MAGNIFICATION Their concentration increases as they move up the food chain
Hint: This is a ring of 6 carbons NOT BENZENE
FUNCTIONAL GROUPS an arrangement of single atoms or groups of atoms, other than carbon or hydrogen, attached to an organic molecule
Halogenated Hydrocarbons Many human-made organic compounds are of this type
One important group of halogenated hydrocarbons is known as CHLOROFLUOROCARBONS (CFC) Invented by chemists in 1920 s to replace toxic compounds used in refrigerators and air conditioning systems
They were praised for being non-toxic and very stable
They were used as fillers in aerosol cans because they are so non-reactive
NAMING HALOGENATED HYDROCARBONS
CFC S AND OZONE DEPLETION In the early 1970s scientists discovered that the ozone layer was becoming depleted There is a natural concentration of OZONE in the stratosphere This ozone layer reflects harmful ultraviolet away from the earth (Recall that ground-level ozone is a pollutant as it irritates the lungs and inhibits photsynthesis)
(not to scale!)
UV radiation is know as IONIZING RADIATION because it can disrupt chemical bonds
Cancer is caused by damage done to the DNA by UV rays.
In the 1980s, satellite images showed a decreasing concentration of ozone, particularly over the poles
It was CFC s that were responsible for depleting stratospheric ozone UV rays release a freeradical of chlorine from the CFC molecule
A single chlorine free radical can cause about 100 000 molecules of ozone to be broken down into oxygen
The damage is worst near the poles because of prevailing winds
The ozone layer is a thin layer of ozone in the atmosphere, 10-50 kilometres above the earth. Ozone has three atoms. It is very rare, only three out of 10 million molecules in the air are ozone. Ninety per cent of ozone is in the upper atmosphere.
In 1987, the United States of America, Canada, Sweden and Norway ban the use of CFCs in aerosols by signing the Montreal Protocol
Many developing countries ask for alternative technologies and financial assistance to implement the Montreal Protocol.
OTHER HALOGENATED HYDROCARBONS Many synthetic products contain halogenated Hydrocarbons like: plastics, fire retardants, paints, solvents, cleaning supplies, pesticides, and herbicides
PCB concentrations have been found to be several times higher than normal in the breast milk of some populations of Canadian Inuit women.
prevailing winds can cause persistent organic pollutants to be come more concentrated at the poles.
ALCOHOLS
Alcohols contain a functional group called a HYDROXYL GROUP The naming is very similar to alkanes just change the suffix to -ol
Systematic Names of Alcohols Old name: Isopropanol Identify and name parent chain Find the functional group Communicate the location of the functional group If there are 2 functional groups, use -diol
Solution Parent chain: propane Functional group on carbon 2 Name: propan-2-ol
Ethan-1,2-diol Propan-1,2,3-triol 2 functional groups 3 functional groups
Naming Alcohols:
CARBOXYLIC ACIDS
Carboxylic acids contain the CARBOXYL FUNCTIONAL GROUP
Acid Name R-COOH indicates the acid functional group in formulas Name of parent chain is changed to oic acid
Carboxylic acids are acids because they donate a proton. They are weak acids, because only a small percentage of acid molecules actually donate their protons.
Identify the two functional groups present in lactic acid.
NAMING CARBOXYLIC ACIDS
Name That Acid
What functional groups? Citric Acid
ESTERS
Esters Formed in the reaction between an alcohol and a carboxylic acid
Esters are made up of an alcohol and an carboxylic acid bonded together The reaction above is called an ESTERIFICATION REACTION
Esters are 2 carbon chains joined by an oxygen atom O R- O- C- R Acid part Alcohol part
NAMING ESTERS
Name?
Identify the acid & alcohol parts Acid part (has the double bonded O) Alcohol part
Alcohol part-acid part Propyl ethanoate
Example Butyl methanoate
Example Draw the structure of pentyl ethanoate
Page 273
More Practice: P.277 Q1,2,4 and 6
Ester Ethyl formate N-amyl acetate N-octyl acetate Methyl butrate Ethyl butrate N-amyl butrate Methyl salicylate Linalyl acetate Flavour Rum Pears, bananas Oranges Apples Pineapples Apricots Oil of wintergreen Lavender, sage The alcohols and acids that form these esters are toxic. For example, methyl butrate gives apples their familiar taste, but methanol is poisonous, and butanoic acid gives rancid butter its odor.
OFFGASSING Many plastics, paints and rubber products release volatile organic compounds into the air.
PESTICIDES Pesticides are evaluated based on: Target specificity Toxicity Persistence Existence/Evolution of resistant strains
LD 50 and LC 50 are common measurements of toxicity One limitation is that they only test the short term effects of toxins
REDUCING THE NEGATIVE IMPACTS OF PESTICIDE USE:
FERTILIZERS AND ORGANIC MATTER
ADDITIONAL NUTRIENTS ADDED TO A SYSTEM nitrates and phosphates from fertilizers or detergents manure from livestock
THE EXCESS NUTRIENTS CAUSE AN ALGAL BLOOM Algae rapidly reproduce because of the extra nutrients
Pigeon Lake 2012
Some types of algae are toxic Toxic blooms can kill fish, other wildlife and even humans Toxic blooms are rare
WHEN THE ALGAE DIES OXYGEN IS DEPLETED: The excess organic matter increases the body of water`s BIOLOGICAL OXYGEN DEMAND (BOD)
WHEN THE ALGAE DIES OXYGEN IS DEPLETED: Decomposing bacteria consume oxygen by cellular respiration If enough oxygen is consumed fish and other aquatic organisms suffocate
BOD Nitrates and phosphates in water can contribute to high BOD levels. Nitrates and phosphates are plant nutrients and can cause plant life and algae to grow quickly. When plants grow quickly, they also die quickly. This dead organic material in the water is then decomposed by bacteria. This results in a high BOD level.
BOD and water temperature water temperature can also cause high BOD levels. As water temperature increases, the rate of photosynthesis by plant life in the water also increases. When the plants die, they fall to the bottom where they are decomposed by bacteria. The bacteria require oxygen for this process so the BOD is high at this location.
Free radicals UV and reactions in the environment can produce free radicals These contain an unpaired electron in the valence level. Can damage cell structures & DNA
Free radicals Antioxidants prevent free radicals from oxidizing compounds in cell structures. Fruits and many vitamins contain antioxidants
Polymers Polymers are large molecules formed from many smaller molecules
Polyester A polymer of ester molecules Dacron
Plastics Material that can be shaped or moulded without heat polymers of alkanes, alkenes, etc. bioplastics are made from renewable sources, such as vegetable fats and oils, or micro-orgnisms.
Review: P 289
P 301
Review P 306-307 19, 20, 21, 23, 26