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Chem Reading Notes Exam 2Chapter 13- 13.5 Types of Organic Reactionso Addition Reactions Two reactants add together to form a single product with no atoms “left over”- A + B  C 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 / \ / \ X Y | | --C≡C-- + 2 X –Y  --C—C-- | | X Yo Elimination Reactions Opposite of addition reactions Single reactant splits into two or more productsX 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 placeX Y \| |/ \ /C—C  C=C + X—Y / \ / \ o Substitution Reaction Two reactants exchange parts to give two new products- AB + C  AC + BH 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 Alkyneso Most of the reactions are addition reactionso A generalized reagent adds to the multiple bond in the unsaturated reactant to yield a saturated product that only has single bondso Simple molecules that are prepared in large quantities are known as chemicalfeedstockso Addition of H 2 to Alkenes and Alkynes: Hydrogenation Alkenes and alkynes react with hydrogen in presence of a metal catalyst 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 acido 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 / \ / \H H Cl Cl Br2 provides a convenient test for presence of carbon-carbon double/triple bonds in a mlcl and also for level of unsaturation of fatso 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 amountso Addition of Water to Alkenes: Hydration  Although a water mlcl could be considered as another type of H—X analkane 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 reactionChapter 14- 14.5 Phenolso Phenol is the name both of a specific compound (hydroxybenzene, C6H5OH) as well as a family of compoundso It can cause severe skin burns and has been found to be toxico Only solutions containing less than 1.5% phenol or lozenges containing a maximum of 50 mg of phenol are now allowed in nonprescription drugso Disinfectant – should be used only on inanimate objects; antiseptic – safely kills microorganisms on living tissueo Phenols have the ability to disrupt the permeability of cell walls of microorganismso Phenols usually named with ending –phenol rather than benzene even thoughstructures include a benzene ringo Properties of phenol influenced by presence of electronegative oxygen atom and hydrogen bonding Water soluble to some degree, but less so than alcohols Higher melting and boiling pts than similarly substituted alkylbenzenesChapter 16- 16.5 Oxidation of Aldehydeso Alcohols are oxidized into aldehydes or ketoneso Aldehydes can be oxidized to carboxylic acids In aldehyde oxidization, the hydrogen bonded to the carbonyl group isreplaced 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 Ketoneso 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 alcoholO O—H || |C  --C—H / \ |aldehyde or ketone Alcoholo Aldehydes are reduced to primary alcohols O OH|| |R—C—H  R—CH2Aldehyde Primary Alcoholo Ketones are reduced to secondary alcoholsO OH || |R—C—R  R—CH—R o These reductions occur by formation of


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UA CHEM 101B - Exam 2

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