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ORGANIC COMPOUNDS CONTAINING OXYGEN, HALOGEN, OR SULFUR. INTRODUCTION. THERE ARE FOUR FAMILIES OF COMPOUNDS THAT CONTAIN A CARBON ATOM SINGLY BONDED TO A HETEROATOM – OXYGEN, HALOGEN, OR SULFUR. ALCOHOLS. ETHERS. ALKYL HALIDES. THIOLS. ALCOHOLS & ETHERS. ARE ORGANIC DERIVATIVES OF H 2 0
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INTRODUCTION • THERE ARE FOUR FAMILIES OF COMPOUNDS THAT CONTAIN A CARBON ATOM SINGLY BONDED TO A HETEROATOM – OXYGEN, HALOGEN, OR SULFUR. ALCOHOLS ETHERS ALKYL HALIDES THIOLS
ALCOHOLS & ETHERS • ARE ORGANIC DERIVATIVES OF H20 • FORMED BY REPLACING ONE OR TWO HYDROGENS ON THE OXYGEN BY ALKYL GROUPS, RESPECTIVELY. • ALCOHOLS CONTAIN A HYDROXYL GROUP BONDED TO A CARBON. • ETHERS HAVE TWO ALKYL GROUPS BONDED TO AN OXYGEN ATOM
ALKYL HALIDES & THIOLS • ALKYL HALIDES CONTAIN A HALOGEN ATOM (X = F, Cl, Br OR I) BONDED TO A CARBON. • THIOLS CONTAIN A SULFHYDRYL GROUP (SH group) BONDED TO A CARBON • A THIOL IS A SULFUR ANALOGUE OF AN ALCOHOL.
PROBLEMS • 14.1 & 14.2
STRUCTURE & PROPERTIES OF ALCHOLS • ALCOHOLS CONTAIN A HYDROXYL GROUP BONDED TO A TETRAHEDRAL CARBON ATOM. • ALCOHOLS ARE CLASSIFIED AS PRIMARY (1o), SECONDARY (2o) OR TERTIARY(3o) • A PRIMARY ALCOHOL HAS AN –OH GROUP ON A CARBON TO 1 CARBON • A SECONDARY ALCOHOL HAS AN –OH GROUP ON A CARBON TO 2 CARBON. • A TERTIARY ALCOHOL HAS AN –OH GROUP ON A CARBON TO 3 CARBON
PROPERTIES OF ALCOHOLS • CONTAINS AN OXYGEN ATOM SURROUNDED BY 2 ATOMS AND 2 LP OF ELECTRONS • BENT SHAPE • BOND ANGLE OF 109.5o • CAPABLE OF INTERMOLECULAR HYDROGEN BONDING. • HAVE HIGHER BPs AND MPs THAN HCs OF COMPARABLE SIZE AND SHAPE • ARE SOLUBLE IN ORGANIC SOLVENTS • LOW MW ALCOHOLS (< 6C) ARE SOLUBLE IN WATER. • HIGHER MW ALCOHOLS (>6C) ARE INSOLUBLE IN WATER
REACTIONS OF ALCOHOLS • Alcohols undergo two useful reactions – DEHYDRATION and OXIDATION. 1. DEHYDRATION DEHYDRATION is an example of a general type of organic rxn called ELIMINATION REACTION ELIMINATION is a reaction in which elements of the starting materials are “LOST” and a new multiple bond is formed.
Zaitsev's rule, Saytzeff's rule or Saytsev's rule • named after Alexander MikhailovichZaitsev(number of different spellings due to the name being transliterated from Russian) is a rule that states that if more than one alkene can be formed during dehalogenation by an elimination reaction, the more stable alkene is the major product. In general, the compound that has a more highly substituted C=C double bond is more stable.
2. OXIDATION OXIDATION results in an increase in the number of C – O bonds or decrease in the number of C – H bonds. • Oxidation occurs by replacing C – H bonds on the carbon bearing the OH group by C – O bonds. • All oxidation products from the alcohol starting material contain a C = O, a carbonyl group • A common reagent for alcohol oxidation is potassium dichromate, K2Cr2O7, a red-orange solid.
Example Primary (1o) alcohols are first oxidized to aldehydes (RCHO), which are further oxidized to carboxylic acids (RCOOH) by replacing one and then two C – H bonds by C – O bonds.
Example Secondary (2o) alcohols are oxidized to ketones (R2CO), by replacing one C – H bond by one C – O bond.
Example Tertiary (3o) alcohols have no H atoms on the carbon with the –OH group, so they are not oxidized.
ETHANOL, THE MOST WIDELY ABUSED DRUG The products of the biological oxidation of ethanol: