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CHM 123 Chapter 23 – Organic Chemistry 23.1 – Organic chemistry and their structures Organic chemistry is the study of carbon containing compounds and their properties. This includes the great majority of chemical compounds on the planet, but some substances such as carbonates and oxides of carbon are considered to be inorganic substances even though they contain carbon. - Organic compounds also may contains O, S, N and halogens Organic Compounds Use mostly covalent bonding Are gases, liquids or solids with low melting points Mostly insoluble in water Many are soluble in organic solvents such as petroleum, benzene and hexane Solution in water generally do not conduct electricity Almost all burn Slow to react with other chemicals Inorganic Compounds Mostly ionic bonding Are generally solids with high melting points Many are water soluble Most are not soluble in organic solvents When dissolved in water conducts electrical current Most not combustible Often undergo fast chemical reactions Two types ◦ Saturated hydrocarbons Dang1 ◦ Unsaturated hydrocarbons Writing Formulas for organic molecules • carbon has 4 valence electrons and hydrogen has 1. carbon achieves an octet by forming four bonds with H or other carbons Structure Presentation E.g. methane: CH4 All single carbon has four bonding position, completely saturated by the four hydrogen atoms. There is only one possible arrangement of the atoms. Condensed formula 2D formula 3D formula CH4 E.g. Ethane: C2H6 Only two carbon atoms are connected to each other and there are six possible bonding sites. These are filled by the six hydrogen atoms Condensed formula 2D formula 3D formula Dang2 E.g. Propane: C3H8 Condensed formula 2D formula 3D formula Because single bonds allow rotation, there are number of ways that alkanes can be drawn using slightly different representation. Constitutional isomers: Compounds that have the same molecular formula but different structural formulas (a different connectivity of their atoms). • For the molecular formulas CH4, C2H6, and C3H8, only one structural formula is possible. There are no constitutional isomers for these molecular formulas. E.g. How many alkane structures can you draw from C4H10? (*Hint: always start with a straight chain carbon-carbon backbone) E.g. How many isomers can you draw from C3H7Cl? * Do cycloalkanes have isomers? YES E.g. There are two possible ways to make ring using four carbon atoms of C4H8. E.g How many constitutional isomer can you draw from C5H10? Dang3 23.2 – 23.3 – Functional groups and naming alkanes IUPAC rules Name # Carbons Condensed formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3 Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH3 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 Alkyl groups: substituents that branch off the main chain. (groups attached to parent) CH3 meth (Me) CH2CH3 ethyl (Et) CH2CH2CH3 propyl (Pr) Dang4 Example Name these alkanes Functional Groups • a characteristic feature of organic molecules that behave in a predictable way. • composed of an atom or group of atoms. • groups that replace a hydrogen atom in the corresponding alkane. • a way to classify families of organic compounds. Dang5 Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. Dang6