What you should remember from last lecture

1. What you should remember from last lecture Organic compounds are based on carbon, and form the basis of biology and of many of the materials that you experience every day. Carbon atoms make 4 covalent bonds, to other carbons and to many other elements in the periodic table. 3. A tremendous array of structures can be made with carbon as a building block, and these structures can display a great range of properties.

2. What you should remember from last lecture Carbons with 4 single bonds are tetrahedral and organic molecules are really 3-dimensional blobs, not flat. Shorthand drawing methods are often used when drawing organic compounds. Remember, carbon makes 4 bonds, whether all 4 are shown or not. Alkanes are simple CnH2n+2 (saturated) hydrocarbons. Cycloalkanes are ring structures with molecular formulae CnH2n. Several isomers (different structures) are possible for most molecular formulae. For practice, can you draw four different hydrocarbons with the molecular formula C6H14? How about four different C5H10 hydrocarbons?

3. What you should remember from last lecture Alkenes and alkynes are hydrocarbons with C-C multiple bonds. These compounds are unsaturated. Petroleum (oil) is the source of a wide array of solvents, fuels, and compounds from which many products can be made. Petroleum refining begins with distillation, which separates the hydrocarbons according to their boiling points. Cracking is a process that breaks larger molecules into smaller, more valuable ones.

4. What you should remember from last lecture • Distillation, cracking, and reforming are essential steps in the refining of petroleum. Distillation accomplishes purification, then the next steps convert the basic component of oil into higher value products. • Coal is composed of much larger molecules, and is much harder to purify and refine. However, there remain vast reserves of coal while petroleum reserves will begin to dwindle soon. • The energy in fuels is stored in chemical bonds. Chemical reactions that change those bonds can liberate energy for use.

5. What you should remember from last lecture • Functional Groups are commonly occurring groups of atoms with characteristic reactivity. The chemical nature of a large, complicated molecule is imply the nature of the ensemble of functional groups. • Halogenated compounds (chlorinated or brominated alkanes, alkenes, and aromatic compounds) have many highly useful properties and are found in many everyday products. Some, particularly halogenated aromatic compounds, are very persistent in the environment.

6. What you should remember from last lecture • Molecular weight, degree of branching, and amount of crosslinking can affect the properties of the resulting polymer. • Polymerization (bond formation between monomers) can be through addition (polyethylene, others) or condensation (polyamides, polyesters). • A plasticizer is often added to a polymer to make it soft and plastic. • Rotation around C=C bonds is difficult. This leads to a new type of isomerism: stereoisomerism cis trans

7. What you should remember from the last lecture • Carbon is not the only element that can form the backbone of a polymer. Silicone has silicon and oxygen as a backbone. • Crosslinked polymers (like epoxy) tend to be hard, inflexible, and durable. • Composite materials are formed when a reinforcing material (glass fiber, graphite fiber) is blended into a matrix material (usually a polymer). Composite materials are usually stiffer and stronger than the pure polymer matrix.

8. What you should remember from last lecture • Oxygen is a common component of organic compounds, appearing in many functional groups, including alcohols, carboxylic acids, and esters. These functional groups appear in many molecules that are important components in personal care products. • Oxygen-containing functional groups tend to make molecules more polar. Hydrocarbons are non-polar. Water will interact strongly with other polar molecules, but not with non-polar (greasy) ones.

9. What you should remember from the last lecture • Fats (triglycerides) can be completely (or partially) converted (saponified) into fatty acids and glycerol, or fatty acids and mono- (or di-) glycerides. • Fatty acids are the basis of soaps. These are effective cleaning agents, as they form micelles with non-polar interiors. Fatty acid salts with calcium are insoluble, and form soap scum. • Alkyl benzene sulfonates, alkyl sulfates and non-ionic surfactants like polyethylene glycol (PEG) are cleaning agents that remain soluble when bound to calcium.

10. What you should remember from the last lecture Some organic molecules are Chiral. Chiral objects are not identical to their mirror images. Molecules that contain a carbon that is bound to 4 different things are usually chiral. Many important biomolecules (molecules of life) are chiral, including most carbohydrates and amino acids, the building blocks of proteins. Carbohydrates (saccharides) are sugars. Simple sugars have the molecular formula Cn(H2O)n. These compounds usually exist as 5- or 6-membered rings containing one oxygen atom.

11. What you should remember from last lecture Simple sugars have the Cn(H2O)n formula. Disaccharides are fomed by condensation of two simple sugar molecules. Polysaccharides are polymers of sugars, and the specific polysaccharide depends on the monosaccharide monomers and how they are linked (position and geometry). Steroids have a characteristic structure consisting of 4 fused rings. Steroids can have potent biological activity as hormones, anti-inflammatory agents, and others.