Ch 25 Chem Guide

• Know hybridization! A typical carbon atom is usually sp3 hybridized • Carbon forms strong bonds: especially with H, O, N and halogens (F, Cl, I…) • Double bonds are stronger than single bonds. Increased bond strength = shorter bond length • Most Carbon-Carbon and Carbond-Hydrogen bonds are nonpolar because the electronegativities almost cancel out. • However C-O and O-H are quite polar • A group of atoms (i.e. C-O-H group) that determines how an organic molecule reacts is called a functional group • The non-polar bonds are generally soluble in nonpolar solvents but not in water • Molecules that are polar are soluble in polar solvents • Acidic substandes: most important are the carboxylic acids (-COOH) • Most important basic substances are the amines (-NHR) (-NH2) of (NR2) o R is an organic group consisting of some combo of C-C and CH bonds such as –CH3 or –C2H5 • Hydrocarbons: compounds composed of only H and C. there are 4 types • Alkanes have only single bonds (saturated hydrocarbons b/c they have the largest # H per C) • Alkenes aka olefins have double bonds • Alkynes have triple bonds • Aromatic hydrocarbond: the C atoms are connected in a planar ring joined by σ and π bonds • All hydrocarbons are relatively nonpolar and insoluble in water • Their boiling points increase as molar mass increases • Alkanes are used as gases • Long chain alkanes generally undergo constant motion that causes it to change its shape like a chain that is shaken • Structural isomers: can be straight chain and branched chain hydrocarbons o Same molecular formula, diff. arrangement • Alkyl groups are named by replacing the –ane ending with –yl • Cycloalkanes are rings sometimes drawn as a polygon in which each corner is a CH2 group (cyclopropane is a triangle) • Aromatic hydrocarbons like benzene have corners with CH groups • Reactions of alkanes: relatively unreactive, unsoluble in water, don’t react with acids, bases, oxidizing agents due to their lack of polarity but they do combust • Unsaturated hydrocarbons • Cis and trans

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cis 2-butene trans 2-butene if a substance contains 2 or more =, each is located by a numerical

suffix (hexadiene) • geometric isomers (cis vs. trans.) • double bonds resist twisting • alkynes are highly reactive but not as commonly found • addition reactions (reactant is added to 2 atoms that form the multiple bond) (replace a double bond with 2 more other atoms) • hydrogenation (replacing a double bond with 2 H’s) • 2 butyne + Cl2 -> trans 2, 3, dichloro 2 butene • aromatic hydrocarbons: a large and important class

• benzene C6H6 • unsaturated, delocalized π bonds causes it to undergo substitution reactions • 3 possible isomers of benzene with 2 nitro groups attached: ortho, meta, and para dinitrobenzene functional groups: (refer to table below) • This study guide basically has everything except the functional groups in terms of R and R’