CHEM 12 - Ch. 12 Alcohols, Phenols, Thiols, & Ethers By...

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By adding oxygen to chains of carbons we produce other important organic compounds: a) alcohols, phenols, ethers (this chapter) b) aldehydes and ketones (Ch. 13) c) carboxylic acids and esters (Ch. 14) The members of this first group are considered organic derivatives of water. If we write water as H—O—H, then an alcohol is R—O—H, a phenol is Ar—O—H, and an ether can either be R—O—R’, R—O—Ar, or Ar—O—Ar” (where R = alkyl group, Ar = aryl group). Alcohols and phenols have characteristic properties due to the –OH (the hydroxyl group ), which is the functional group for these classes of compounds, and this is the site where most reactions occur. Thiols is the class of compounds which contain the sulfhydryl group (--SH), and these have a structure similar to those of alcohols. Carbohydrates, lipids, and proteins contain –OH and/or –SH groups. Classification and Naming of Alcohols Alcohols are grouped in the following 3 classifications: a) primary : the –OH bearing carbon bonded to no (this is methanol) or 1 other carbon atom b) secondary : the –OH bearing carbon bonded to 2 other carbons c) tertiary : the –OH bearing carbon bonded to 3 other carbons The chemical and physical properties of alcohols depend greatly on what classification they fall under. The IUPAC rules for naming alcohols are as follows: 1) Identify and name the longest carbon chain (LCC) with the attached hydroxyl group. Drop final –e from the parent alkane and replace it with the suffix –ol . 2) Number the carbons to give the –OH bearing carbon the lowest #. 3) Locate and name any other substituent groups on the chain. 4) If more than one –OH group appears on the same molecule, the suffixes –diol , -triol , etc. are used with the –e ending of alkane.
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Physical Properties of Alcohols Alcohol molecules can associate with one another or with water molecules through hydrogen bonding, which has profound effects on an alcohol’s physical state at room temperature and its solubility. When comparing the alcohol and the alkane with the same # of C’s, the alcohol usually has the higher boiling point (BP). Examples are: BP of CH 3 OH is 65°C versus BP of CH 4 is -164°C, BP of CH 3 CH 2 OH is 78°C versus BP of CH 3 CH 3 is -89°C, BP of CH 3 CH 2 CH 2 OH is 97°C versus BP of CH 3 CH 2 CH 3 is -42°C. For these short carbon chain alcohols (which are liquids at RT), they are soluble in water, while the C1-C3 alkanes (gases) are insoluble. As the length of the C chain increases, water solubility decreases.
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This note was uploaded on 04/09/2008 for the course CHEM 104 taught by Professor Nathan during the Spring '08 term at St. Francis PA.

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CHEM 12 - Ch. 12 Alcohols, Phenols, Thiols, & Ethers By...

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