OCHEM_I_UNIT_14 - OCHEMIUNIT14:ALKYNES A.INTRODUCTION...

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OCHEM I UNIT 14: ALK Y NES A. INTRODUCTION                                             1. DEFINITION -Alkynes  are  unsaturated   hydrocarbons  that contain at least one  C-C  triple bond. 2. GENERAL MOLECULAR FORMULA OF ALK Y NES   C n H 2n-2 n = number of carbon atoms in molecule. Note: -have a homologous series. Ex:  n = 1 n = 2 n = 6 n = 10 1
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3. TYPES OF ALK Y NES: 4 types  a. Terminal Alkynes b.   Internal alkynes c. Symmetrical alkynes d. unsymmetrical alkynes 4. PROPERTIES OF THE C-C TRIPLE BOND The  -C C-  is a very rigid bond. It cannot be rotated like a single bond.  B. NAMING ALKYNES  1. IUPAC NAMES 2
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-Same rules as alkenes, except the names of alkynes end in – yne  (or  - diyne ). 2. ISOMERISM IN ALKYNES n =  4  CH 3 CH 2 C C-H 1-butyne CH 3 C CCH 3 2-butyne 3. POLYYNES Polyynes are alkynes with 2 or more triple bonds.  H-C CCH 2 CH 2 CH 2 C C-H 1,6-heptadiyne 4. COMMON NAMES Alkynes are named as  acetylenes. n Molecular formula name structure 2 C 2 H 2 eth yne H-C C-H 3 C 3 H 4 prop yne CH 3 C C-H 4 C 4 H 6 but yne CH 3 CH 2 C C-H 4 C 4 H 4 1-but en -3- yne CH 2 ‚ CHCC C-H Structure IUPAC Common name H-C C-H ethyne acetylene CH 3 C C-H propyne Methyl acetylene CH 3 C CCH 3 2-butyne Dimethyl acetylene CH 2 ‚ CHCC C-H 1-buten-3-yne Vinyl acetylene 3
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5. ALKYNYL GROUPS CH 3 CH 2 C C- 1-but ynyl HC C- eth ynyl Ex: C C H Ethynylcyclopropane Do problems on pages 401 – 403. Note: Small ring cycloalkynes are unstable . Cyclooctyne is the lowest  cycloalkyne ever isolated. However, it is unstable.  Read page 402. C. PHYSICAL PROPERTIES OF ALKYNES  Like the alkanes and alkenes, alkynes are nonpolar. Therefore, they have  only weak VWF between their molecules. As a result, they have physical  properties similar to those of the other hydrocarbons (Low BP, MP,  insoluble in water, etc.) D. IMPORTANT ALKYNES  4
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See Fig. 11.2 page 404. See pages 403.  -acetylene -ethynylestradiol (looks like estradiol; prevents ovulation) and  norethindrone (looks like progesterone; induces the production of a  thick mucus that prevents the sperm to reach the uterus) = Birth 
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This note was uploaded on 04/19/2011 for the course CHEMISTRY 2423 taught by Professor Kay during the Spring '08 term at Dallas Colleges.

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OCHEM_I_UNIT_14 - OCHEMIUNIT14:ALKYNES A.INTRODUCTION...

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