CHAPTER 7 NOTES

CHAPTER 7 NOTES - CHAPTER 7 ALKENES& ALKYNES PROPERTIES...

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Unformatted text preview: CHAPTER 7 ALKENES & ALKYNES: PROPERTIES, SYNTHESIS-- INTRODUCTION-- NOMENCLATURE: “ E – Z ” SYSTEM-- STABILITY : ∆ H ° OF – HYDROGENATION – COMBUSTION-- SYNTHESIS OF ALKENES -- FROM: – R- X – R- OH – >C X-C X <-- SYNTHESIS OF ALKYNES -- FROM: – -C H X-C H X- – -C H 2-C X 2- – TERMINAL ALKYNES OF LOWER MW-- HYDROGENATION OF ALKENES-- HYDROGENATION OF ALKYNES-- INDEX OF HYDROGEN DEFICIENCY INTRODUCTION: > C = C < – C ≡ C – ALK E NE ALK Y NE C n H 2n C n H 2n - 2-- HYBRIDIZATION ?-- BOND ANGLES ?-- POLARITY ? SO ?-- SOLUBILITY IN: – WATER ? – BENZENE ? – HEXANE ?-- DENSITY ? NOMENCLATURE: “ E – Z ” SYSTEM ( REALLY ! ) ☺-- BASIC NOMENCLATURE RULES: REVIEW ( CHAPTER 4 ) HOWEVER, MANY TIMES, THESE RULES ARE NOT ENOUGH !- WHY ?-- ROTATION ABOUT >C =C< IS RESTRICTED ( NOT “ FREE ” ! ) SO ? v GEOMETRIC ISOMERS MAY BE POSSIBLE: vi ( DIASTEREOMERS ) SO ?-- NEED A SYSTEMATIC WAY TO DISTINGUISH BETWEEN THEM !-- DI SUBSTITUTED ALKENES : CIS , TRANS CIS - TRANS – ( SAME SIDE ) ( OPPOSITE SIDE ) -- TRI SUBSTITUTED ALKENES: o o CANNOT USE “ CIS ” OR “ TRANS ” TO DISTINGUISH BETWEEN THESE SO ? NEED MORE SPECIFIC NAME USE “ E – Z ” SYSTEM ! ☺ HOW ? USE: CAHN – INGOLD – PRELOG RULES-- AT EACH sp 2 – C , PRIORITIZE THE TWO GROUPS ACCORDING TO ATOMIC NUMBER AS: ( I ) & ( 2 ) HIGHER AT. NO. = HIGHER PRIORITY = 1 LOWER AT. NO. = LOWER PRIORITY = 2-- THEN DETERMINE WHETHER THESE PRIORITIES ARE ARRANGED R H R H H R R H H H 3 C Cl Br H Br Cl H 3 C “ CIS ” – LIKE : “ Z ” ISOMER OR “ TRANS ” – LIKE : “ E ” ISOMER-- DO PROBLEM : 7.1 p. 289 STABILITY : ( RELATIVE ! )-- SEE FIG. 7.1, 7.2 p. 290, -- HEATS OF HYDROGENATION NOTE: HYDROGENATION MUST RESULT IN THE FORMATION OF THE SAME PRODUCT(S) i.e. , ALKENES BEING COMPARED MUST HAVE IDENTICAL CARBON SKELETONS ( POSITION OF C=C MAY BE DIFFERENT )-- HEATS OF COMBUSTION-- SEE p. 291 NOTE: COMBUSTION RESULTS IN THE FORMATION OF THE SAME PRODUCT(S) EVEN IF ALKENES BEING COMPARED DO NOT HAVE IDENTICAL CARBON SKELETONS IN GENERAL: STABILITY % DEGREE OF SUBSTITUTION-- DO PROBLEMS : 7.2, 7.3, 7.4 p. 291-- CYCLOALKENES-- SEE FIG. 7.3 – 7.5 p. 292-- CIS v. TRANS : RING SIZE ? SYNTHESIS OF ALKENES:-- SEE p. 292-- DEHYDROHALOGENATION OF : R – X-- STRONG BASE-- HIGH TEMPERATURE ( WHY ? ) ( WHY THESE CONDITIONS ? ) FACILITATE E2 ! C C X H C C OH H C C Br Br ? ? ?-- REGIOCHEMISTRY : -- LOCATION OF DOUBLE BOND IN PRODUCT-- SOMETIMES, MORE THAN ONE PRODUCT IS POSSIBLE !...
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This note was uploaded on 04/14/2008 for the course CHEM 2370 taught by Professor Dandekar during the Fall '07 term at North Texas.

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CHAPTER 7 NOTES - CHAPTER 7 ALKENES& ALKYNES PROPERTIES...

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