Chem Reading Notes Exam 2 Chapter 13 13 5 Types of Organic Reactions o Addition Reactions left over A B C Two reactants add together to form a single product with no atoms Most common rxns are when a reagent adds across a carbon carbon multiple bond to give a product that contains two for alkenes or four for alkynes new single bonds X Y C C X Y C C C C 2 X Y C C X Y X Y o Elimination Reactions Opposite of addition reactions Single reactant splits into two or more products X Y A B X Y A B Converts starting material to product that has two fewer single bonds and a carbon carbon multiple bond in their place X Y C C C C X Y o Substitution Reaction Two reactants exchange parts to give two new products AB C AC B H H H C H Cl Cl H C Cl H Cl H H CH3CH2CH2Cl CH3O Na CH3CH2CH2OCH3 Na Cl o Rearrangement Reactions Rearrangements are of bonds and atoms to yield a single product that is an isomer of the reactant Y X X Y C C C C 13 6 Reactions of Alkenes and Alkynes o Most of the reactions are addition reactions o A generalized reagent adds to the multiple bond in the unsaturated reactant to yield a saturated product that only has single bonds o Simple molecules that are prepared in large quantities are known as chemical feedstocks o Addition of H catalyst 2 to Alkenes and Alkynes Hydrogenation Alkenes and alkynes react with hydrogen in presence of a metal Addition of hydrogen to an alkene is called hydrogenation It is used to convert unsaturated vegetable oils to saturated fats used in margarine and cooking fats Creates trans fatty acid o Addition of Cl 2 and Br2 to Alkenes Halogenation Alkenes react with halogens Br2 and Cl2 to give 1 2 dihaloalkane addition products in a halogenation rxn H H H H C C Cl2 H C C H Cl Cl H H Br2 provides a convenient test for presence of carbon carbon double triple bonds in a mlcl and also for level of unsaturation of fats o Addition of HBr and HCl to Alkenes Alkenes react with hydrogen bromide to yield alkyl bromides and hydrogen chloride to yield alkyl chlorides H C C H H Br Cl When HBr and HCl add to an alkene in which one of the double bond carbons has more hydrogens than the other results can be predicted by Markovnikov s rule Marknovnikov s rule In the addition of HX to an alkene the major product arises from the H attaching to the double bond carbon that has the larger of H atoms directly attached to the it and the X attaching to the carbon that has the smaller number of H atoms attached Explanation has to do with stability of intermediates known as carbocations that form during reaction If an alkane has equal numbers of H atoms attached to the double bond carbons both possible products are formed in approximately equal amounts o Addition of Water to Alkenes Hydration Although a water mlcl could be considered as another type of H X an alkane will not react with pure water alone If a small amt of strong acid catalyst such as H2SO4 is added an addition rxn takes place to yield an alcohol This is a hydration reaction o Phenol is the name both of a specific compound hydroxybenzene C6H5OH as well as a family of compounds o It can cause severe skin burns and has been found to be toxic o Only solutions containing less than 1 5 phenol or lozenges containing a maximum of 50 mg of phenol are now allowed in nonprescription drugs o Disinfectant should be used only on inanimate objects antiseptic safely kills microorganisms on living tissue o Phenols have the ability to disrupt the permeability of cell walls of o Phenols usually named with ending phenol rather than benzene even though o Properties of phenol influenced by presence of electronegative oxygen atom microorganisms structures include a benzene ring and hydrogen bonding Water soluble to some degree but less so than alcohols Higher melting and boiling pts than similarly substituted alkylbenzenes Chapter 14 14 5 Phenols Chapter 16 16 5 Oxidation of Aldehydes o Alcohols are oxidized into aldehydes or ketones o Aldehydes can be oxidized to carboxylic acids In aldehyde oxidization the hydrogen bonded to the carbonyl group is replaced by an OH group Aldehydes typically have a musty odor due to their partial oxidation to carboxylic acids O O R C H R C OH o Ketones because they don t have the hydrogen do not react cleanly with oxidizing agents no reaction Because ketones cannot be oxidized treatment wit ha mild oxidizing agent is used to test to distinguish between aldehydes and ketones Tollen s reagent o Benedict s reagent does not unequivocally distinguish between ketones and aldehydes 16 6 Reduction of Aldehydes and Ketones o The reduction of a carbonyl group occurs with the addition of hydrogen across the double bond to produce an OH group This is the reverse of the oxidation of an alcohol O C C H O H aldehyde or ketone Alcohol o Aldehydes are reduced to primary alcohols O OH R C H R CH2 Aldehyde Primary Alcohol o Ketones are reduced to secondary alcohols O R C R R CH R OH o These reductions occur by formation of a bond to carbonyl carbon atom by a hydride ion H accompanied by a bonding of a hydrogen ion H to the carbonyl oxygen atom This is logical because the polarity of the carbon group O H attracted here C H attracted here The hydride ion has a lone pair of valence electrons so it is attracted to the polar and positive C atom The hydrogen ion has a positive charge so it is attracted to the polar and negative O atom These two hydrogen atoms come from different sources Chapter 17 17 4 Reactions of Carboxylic Acids Ester and Amide Formations o Reactions of alcohols and amines with carboxylic acids both result in substitution of other groups for the OH of the acid and formation of water as a by product With alcohols the OH of the acid is replaced by the OR of the With amines the OH of the acid is replaced by the NH2 NHR or alcohol NR 2 of the amine o Esterification O R C OH H OR R C OR H2O O Carboxylic acid an alcohol an ester water Ester formation is called esterification Done by warming carboxylic acid with an alcohol in presence of a strong acid catalyst such as sulfuric acid o Amide Formation Esterification reactions are reversible and often reach equilibrium with approximately equal amounts of both reactants and products present Ester formation is favored either by using a large excess of the alcohol or by continuously removing one of the products O O O R C OH H NR 2 R C NR 2 H2O Unsubstituted amides are formed by the reaction of carboxylic acids with …