Carbon’s Key Properties • Has a mid-range electronegativity value so it forms covalent bonds and shares electrons • Can form a maximum of four bonds • Can form chains, sheets, and rings • Usually combined with H and often bonds with O, S, N and P
HYDROCARBONS Carbon Skeletons and Hydrogen Skins Each C can form a maximum of four single bonds, OR two single and one double bond, OR one single and triple bond. The arrangement of C atoms determines the skeleton, so a straight chain and a bent chain represent the same skeleton. Groups joined by single bonds can rotate, so a branch pointing down is the same as one pointing up.
The Other Carbon Bonds • If carbon is not bound to anything else in an organic compound, it will be attached to hydrogen. C – C – C – C – C | C
C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C ring Some five-carbon skeletons. single bonds double bond
Saturated and Unsaturated • When the carbon in organic compounds forms only single bonds we say that the compound is saturated (can’t add anything more). • If there are double or triple bonds, these can be broken to add more atoms. In this case we say that the compound is unsaturated.
Isomers • When two compounds have the same chemical formula but different structural formulas they are called isomers. • There are many kinds of isomers depending on where the carbons are placed and how bonds are arranged.
Isomers and Vision • If you take beta carotene and split the molecule, you get 2 Vitamin A molecules. These are related to retinal. • Retinal changes form when a photon of light strikes it. • http://www.elmhurst.edu/~chm/vchembook/531vision.html
Depicting cycloalkanes. cyclobutane cyclopropane
methanal (formaldehyde) used to make resins in plywood, dishware, countertops; biological preservative ethanal (acetaldehyde) narcotic product of ethanol metabolism; used to make perfume, flavors, plastics, other chemicals benzaldehyde artificial almond flavoring 2-butanone (methyl ethyl ketone) important solvent 2-propanone (acetone) solvent for fat, rubber, plastic, varnish, lacquer; chemical feedstock Some common aldehydes and ketones.
methanoic acid (formic acid) an irritating component of ant and bee stings butanoic acid (butyric acid) odor of rancid butter; suspected component of monkey sex attractant benzoic acid calorimetric standard; used in preserving food, dyeing fabric, curing tobacco octadecanoic acid (stearic acid) found in animal fats; used in making candles and soap Some molecules with the carboxylic acid functional group.
cetyl palmitate the most common lipid in whale blubber tristearin typical dietary fat used as an energy store in animals lecithin phospholipid found in all cell membranes Some lipid molecules with the ester functional group.
Polymers • Long chain molecules made of small repeating units • Can be made by addition reactions (adding molecules) or condensation (splitting something out and joining the pieces. • Building polymers….
Crosslinking • Some polymers make bridges across chains rather than just adding to chains. These are “cross-linked” polymers. • Some cross-links are covalent bonds and are permanent. Some links are made with intermolecular forces and can be broken more easily (like the alginate worms).