FSN 1500 Week 7

1. FSN 1500 Week 7 Organic Compounds, the Periodic Table and Related Topics

2. Organic Compounds • Organic compounds - carbon-containing compounds where carbon forms the structural framework of the molecule • Remember: to our knowledge all life on Earth is organic compound based! • Millions of organic compounds exist; organic compounds are over 10X more abundant than all inorganic compound types combined • Why are there so many organic compounds if carbon atoms comprise only 0.02% of crustal elements by weight?

3. Organic Compounds • Organic compounds are so abundant because carbon can bond to other atoms by a variety of mechanisms, has a small atomic volume and tends to form strong covalent bonds in organic molecules • Organic compounds are classified into a variety of categories; the simplest organic compounds are the hydrocarbons

4. Organic Compounds (Hydrocarbons) • Hydrocarbons - compounds containing different ratios of hydrogen and carbon atoms • The methane series of hydrocarbons (see figure) contains many useful fuel gases, gasoline, kerosene and waxes

5. The methane series of hydrocarbons

6. Organic Compounds • All organic compounds can have their molecular structures represented through Lewis Structures • The line segment between atoms represents a single covalent bond (one pair of electrons shared) Butane (C4H10) Lewis Structure Diagram

7. Organic Compounds • Lewis Structures provide insight into the physical and chemical behavior of a compound (remember: a compound’s properties are dictated by its composition, type of bonding and bond orientation) • Isomers - organic chemical compounds with the same formula but different molecular structures; the different structures result in different properties! (see figure)

8. Isomers – organic chemical compounds with the same chemical formula but different molecular structures. Note how the different structures results in different properties for the isomers.

9. Organic Compounds (Hydrocarbons) • Hydrocarbons can be subclassified into alkane, alkene and alkyne families • Alkane hydrocarbons host single electron pair covalent bonds between atoms - sometimes referred to as saturated hydrocarbons; all alkanes have the generic formula (CnH2n+2) (see figure) • The more saturated the compound the less chemically reactive it is (e.g., saturated fats)

10. Alkane Hydrocarbons

11. Organic Compounds (Hydrocarbons) • Alkene hydrocarbons - category of hydrocarbons that share the general formula CnH2n (e.g., C2H4 - ethylene gas); these possess at least one double covalent bond (two electron pairs shared) between adjacent carbon atoms (see figure)

12. Alkene Hydrocarbons note the double covalent bond

13. Organic Compounds (Hydrocarbons) • Alkyne hydrocarbons - category of hydrocarbons that share the general formula CnH2n-2 (e.g., C2H2 - acetylene gas); these possess at least one triple covalent bond (three electron pairs shared) between adjacent carbon atoms (see figure) • Alkanes are saturated hydrocarbons, the alkenes and alkynes are unsaturated and more chemically reactive

14. Alkyne Hydrocarbons Why are the alkenes and alkynes more chemically reactive than the alkanes? Think about the relative length and strength of the covalent bonds in these compounds.

15. Bond Length and Bond Strength Comparison for a Single Covalent Bond Covalent Bond A Covalent Bond B N N N N Bond Length Bond Length N = atomic nucleus The longer the bond length the weaker the bond.

16. Butane Acetylene The bond length of the single covalent bonds in Acetylene is longer, and therefore weaker, than the bond length of the single covalent bonds in Butane

17. Organic Compounds (Hydrocarbons) • Aromatic hydrocarbons - category of pleasant smelling unsaturated hydrocarbons with structures derived from that of the benzene ring (C6H6 - see figure) • Many aromatic hydrocarbons are toxic or thought to be carcinogenic even in small amounts (e.g., PBB - polybrominated biphyenl, PCB - polychlorinated biphyenl)

19. Polychlorinated Biphenyls Two benzene rings bonded together = a “biphenyl”

20. Organic Compounds (Hydrocarbons) • Aromatic hydrocarbon contamination of public water supplies, soil, fish and other natural resources is common in most industrial areas since the aromatic hydrocarbons or their byproducts are common in industrial products or their wastes Many older electrical transformers contain PCBs in the electrical insulating fluids

21. Organic Compounds (Alcohols) • Alcohols - organic compounds similar to the hydrocarbons, but one or more of the H atoms is replaced by an hydroxide (OH) group (see figure)

22. Organic Compounds (Alcohols) H H H OH H C C H OH C H H H Ethanol Methanol

23. Organic Compounds (Alcohols) • The OH group is called a “functional group”; functional groups are the chemical constituents that most determine the properties of that substance • Example: What’s the only Lewis Structure difference between methane (CH4 - hydrocarbon) and methanol (CH3OH - alcohol)?

24. Organic Compounds (Organic Acids) • Organic acids - organic compounds that generate acidic solutions; the functional group for these compounds is the carboxyl group (COOH); acetic acid (the acid of vinegar) is an example; see figure • Organic acids are produced from decaying organic matter and may be important agents of chemical weathering

26. Organic Compounds (Fats) • Fats - organic compounds that belong to a broader category called esters; esters are formed by the reaction between an alcohol and an acid (see figure) • Solid fats are saturated; the fats in liquid oils are technically unsaturated - be careful: some cooking oils have small particles of solid fat blended into them

28. Organic Compounds (Fats) • Why do nutritionists advise that our fat intake is low (< or = 30% of caloric intake) and that we limit our intake of saturated fats? • What is hidden in the terms “partially hydrogenated oil ” and trans-fatty acids? • What is the controversy surrounding trans-fats in the food supply and what recent legal actions illustrate the importance of this topic for the layperson?

29. Organic Compounds (Fats) What is hidden in the terms “partially hydrogenated oil ” and trans-fatty acids? What is the controversy surrounding trans-fats in the food supply and what recent legal actions illustrate the importance of this topic for the layperson?

30. Organic Compounds (Carbohydrates) • Carbohydrates - organic compounds whose formulas look like they contain carbon united with water ; consist of C, H, and O atoms with H atoms twice, or nearly, the number of O atoms • There are many carbohydrates; they’re generally classified as “simple” – relatively few atoms per molecule (e.g., glucose - C6H12O6 and other sugars) or “complex” (perhaps dozens to thousands of atoms per molecule) (see figure)

32. Organic Compounds (Carbohydrates) • Complex carbohydrates may contain hundreds of atoms per molecule - these include starches found in foods like rice, potatoes, oatmeal, etc. • Why do nutritionists advocate that our diets be based on complex carbohydrates, not simple carbohydrates?

33. Organic Compounds (Carbohydrates) • The aerobic decomposition of carbohydrates in our body is a primary energy producer: CH2O(s) + O2(g) ---> CO2(g) + H2O + energy • Proteins - organic compounds that contain the amino (NH2) functional group and usually a little sulfur or phosphorous • Proteins are constructed by the linking of amino acids (organic acids containing the amino group) into chains (see figure)

35. Organic Compounds (Proteins) • Some proteins may be composed of chains containing tens of thousands of amino acids • Nutritionists often refer to essential (supplied by our diet) and non-essential (manufactured in the body) amino acids; proteins are involved in nearly every biological process

36. The Periodic Table • Chemists of the eighteenth and nineteenth century noticed that certain elements (e.g., Au, Ag, Cu or He, Ne, Ar) exhibited similar chemical behavior • Mendeleev (Russian) and Meyer (German) proposed that the chemical behavior of elements was a periodic (recurring) function of their atomic masses

37. The Periodic Table • Mendeleev published one of the first periodic tables in 1872 (see figure) • Mendeleev and Meyer didn’t have knowledge of subatomic structure - their ideas were subsequently modified

39. The Periodic Table • Modern Periodic Law - the chemical behavior of the elements is a periodic function of their atomic number • We now know that the electron distribution around the nucleus controls the atom’s chemical behavior. In an uncharged atom what controls the number of electrons? The number of protons (atomic number) in the nucleus. • The modern periodic table is arranged into an array (series of rows and columns) of increasing atomic number elements

40. The Periodic Table • The rows of the periodic table are called periods; the columns are called families or groups (see figure) • All the members of a group have the same outermost energy level electron distribution pattern - the reason for their similar behavior • Metals are the most abundant elements ; the true nonmetals lie toward the far and upper right of the table

42. The Periodic Table • A few elements (e.g., As, Po) are called metalloids - they have properties of both metals and nonmetals • Across a period (left to right) the properties of the elements trend from strongly metallic to strongly non-metallic with the last member of each period a noble gas

43. The Periodic Table • Brief Overview of Some Groups: • Noble Gases (VIIIA) - all have the electron distribution required for energetic stability and therefore have no tendency to chemically react • Halogens (VIIA) - all need one electron to complete their energy stability requirements; hal - salt, gen - genesis

44. The Periodic Table • The halogens commonly react with elements that need to lose one electron to become energetically stable: Na1+ + Cl1- NaCl (table salt) • The alkali metals (IA) are metals that react with water to form alkaline (basic) solutions; they commonly react with the halogens

45. The Periodic Table • The alkaline earth metals (IIA) commonly react with oxygen to form heat-resistant oxides; the term earth is an historic one that implies a heat-resistant oxide • If you understand the periodic table you can make predictions about what elements should be able to form simple compounds; you can also answer what seem to be unrelated questions.

46. The Periodic Table • Questions such as: • Why is He and not H gas used as a dirigible floatation gas? • Why did radioactive Sr particles in the fallout from nuclear weapons testing lead to a ban on above-ground nuclear testing? • Why did one of the original Star Trek episodes involve a creature composed of Si?

47. The Periodic Table • Other points of interest: • Heavy elements (metals) - elements that are “biologically heavy” ; our bodies can’t effectively secrete them through the urine, feces, or perspiration. Examples: As, Hg, Pb, Al. These may accumulate in the body and produce toxic response. They especially adversely affect the Central Nervous System. How does this relate to the Mad Hatter in “Alice in Wonderland”? • Since 2007, what possible source of lead (Pb) contamination has many U.S. parents worried?

48. The Periodic Table • Note in the following slides how residual lead poisoning is still problematic in many U.S. cities and that higher bone-lead levels have also been linked to an increase incidence in teen criminal delinquency

49. Lead Sources? Soil, pre-1980s paints, lead municipal water pipes (Detroit), old lead smelters (Detroit) Source: Geotimes, May 2005

50. Neighborhoods to get additional lead tests March 10, 2004 BY WENDY WENDLAND-BOWYER AND TINA LAMFREE PRESS STAFF WRITERS The Michigan Department of Environmental Quality plans to conduct hundreds of tests in two neighborhoods with dangerously high levels of lead in the soil to find out whether it came from former lead smelters. The two neighborhoods -- one in Hamtramck and the other in Detroit -- are downwind from possible old lead smelters, according to the DEQ report released late Tuesday. The state tested the soil on publicly-owned property in residential neighborhoods near 10 former smelting sites late last year. Almost all the sites had high levels of lead in the soil. Three sites had high lead levels where the wind would have carried it if it had come from the old smelters, the report said. The other seven sites either showed high lead levels in no particular pattern or low lead levels.