1.4 Alcohols

ALCOHOL an organic compound that contains a hydroxyl group (-OH) named using the parent alkane and ending in “ol” alcohols are POLAR molecules the C-O bond is polar and so is the O-H bond!

THREE CLASSES OF ALCOHOLS: PRIMARY SECONDARY TERTIARY - OH bonded to terminal C atom -OH bonded to C atom with 2 alkyl groups attached -OH is bonded to a C atom with 3 alkyl groups

NAMING ALCOHOLS use the parent alkane, drop -e and add –ol (keep the “e” if it has more than 1 hydroxyl group) include the carbon number to which -OH attaches (unless it is cyclic…then it is #1 by default) if there are hydrocarbon or halide substituents, give the lowest number carbon to the hydroxyl (-OH) group preferentially

ISOMERS OF ALCOHOLS

POLYALCOHOLS contain more than one -OH group

CYCLIC HYDROCARBONS can also form alcohols use the root name of the cyclic HC and add the suffix -ol

AROMATIC HYDROCARBONS can have -OH groups added, forming an aromatic alcohol Right example: can be called 1,2-dihydroxybenzene, benzene-1,2-diol, ortho-benzenediol (ortho 1,2; meta 1,3; para 1,4)

EXAMPLE 1: Name and identify the type of alcohol.

EXAMPLE 2: Draw the structure of butane-1,3-diol

PRACTICE TIME! p. 34 #1 & 2

PROPERTIES OF ALCOHOLS #1) Alcohols have much higher boiling points than the corresponding alkanes METHANOL METHANE BP = 65 C BP = -162 C polar molecule nonpolar molecule - strong dipole-dipole forces - H bonding between OH groups of adjacent molecules - weak VDW forces

PROPERTIES OF ALCOHOLS #2) The shorter the carbon chain, the more soluble the alcohol because the -OH group increases polarity. But if the HC chain is very long, it causes the entire molecule to become nonpolar. Usefulness as a solvent???

REACTIONS OF ALCOHOLS

1. Preparation of Methanol carbon monoxide + hydrogen gas= methanol (INDUSTRIAL PROCESS) breakdown of organic matter by anaerobic bacteria (natural process) 2. Preparation of Ethanol (fermentation) sugar from beets, corn, or sugar cane + yeast = ethanol + carbon dioxide (natural process- called fermentation) ethene + water= ethanol (addition reaction)

3. Combustion of Alcohol (Propanol) ALL organic matter can undergo complete combustion in the presence of oxygen (products: CO2 + H20 ) or incomplete combustion when oxygen concentration is low (products also include C(s)- soot, and toxic carbon monoxide, CO (g)) 4. Hydration (remember Markovnikov’s rule!) When adding H-X to an alkene, the H goes preferentially to the carbon that already has more H-s. cis-2-bromobut-2-ene + H20 = 2-bromobutan-2-ol

5. Dehydration of Alcohols from Alkenes + water removes a hydrogen atom and a hydroxyl group catalyzed by H2SO4

EXAMPLE 1: Write the chemical equation of the addition reaction of pent-1-ene and water

EXAMPLE 2: Write the chemical equation of the dehydration of ethanol.

HOMEWORK: practice p. 37 #1&2