NEW!
I/EC
REPORTS
Polymers Sewed up Newly found methods to determine tacticity point the w a y to tailor-made polymers I ACTICITY of polymers c a n n o w be
QO* DIHYDROPYRAN (2,
3-dihydro-4H-pyran)
A new development chemical from
The Quaker Oats Company Q O D i h y d r o p y r a n is a c o l o r l e s s , m o b i l e liquid of e t h e r - l i k e o d o r . I t is v e r y r e a c t i v e ; t h e a c t i v i t y is c e n t e r e d a r o u n d t h e double bond.
CHEMICAL
PROPERTIES
Dihydropyran exhibits properties of a vinyl ether. It adds hydrochloric and hydrobromic acids to form the corresponding 2-halotetrahydropyran. Alcohols add readily to the double bond in the presence of acids; thus addition of methanol forms 2-methoxytetrahydropyran, an acetal from which the alcohol may be readily regenerated by hydrolysis. Here, then, is a method of protecting alcohol groups during reactions. Reactions of dihydropyran with water in the presence of acid or an acidic ion exchange resin results in 2-hydroxytetrahydropyran, the cyclic form of (5-hydroxypentanal. Our Bulletin 137 describes many more reactions, and gives references. PHYSICAL·
P R O P E R T I E S (pure compound) Specific G r a v i t y , 20, 4 ° C . 0.927 B o i l i n g Point. ( 7 6 0 m m . ) " C . 84.3 Freezing P o i n t . ° C . -70 Solubility, 25°C. 1.6 g./ 100 g. water g. water 100 g. d i h y d r o p y ran 0.5 W a t e r azeotrope 9.8 % water ( b . 7 1 - 2 ' C . ) Flash P o i n t , T . ( T a g . closed cup) 0 V a p o r Pressure =C. mm. of Hg. 0 34.9 10 57.0 30 148.0 302.0 50 70 600.0
determined. This means empirical concepts are about dead in polymer chemistry a n d the way is clear for a major forward step in t h e science: Catalog t h e basic parameters which predict structure and store these d a t a in data-processing machines or other devices. A p p r o p r i a t e searching will give the information needed to tailorm a k e polymers. For years, macromolecules were m a d e a n d characterized on the basis of end groups, branching, molecular weights, a n d molecular weight dis tribution. But the work of Zieglcr, N a t t a , and others pointed to another factor : stereospecific regulation— how a r e polymer substituents a r ranged? H o w m u c h is isotactic, syndotactic, or heterotactic? These questions called for n e w methods to characterize polymers— methods which deal with details of chain structure. These details a r e i m p o r t a n t , for they influence be havior—for example, melting point, rigidity, strength, a n d resistance t o solvents. And, chain structure d e tails also reveal the shape of m a c r o molecules in t h e crystalline state— whether they a r e plain, zigzag, or hélicoïdal. At the Division of Polymer C h e m istry several of t h e needed methods c a m e to light, a m o n g them : •
Hydrolysis of crystalline acrylic polymers by both alkalies a n d acids. T h e former is d o n e in an aqueous alcoholic m e d i u m in which the hydrolyzate is insoluble; the latter i n a h o m o geneous solution in aqueous acetic acid. T h e m e t h o d is a way to identify t h e different crystalline types of polymers.
•
Nuclear magnetic resonance was used by Minnesota M i n i n g
QO Dihydropyran is available in 55 gallon drum quantities (net weight 375 pounds) f.o.b. Memphis, Tennessee. Write for our Bulletin 137.
The Quaker Oa's Company
The Quaker Oats Company CHEMICALS
%
36 A
ΤΠΤ
DIVISION
337D The Merchandise Mart, Chicago 5 4 , Illinois Room 437D, 120 Wall Street, New York 5, New York Room 537D, 48 5.E. Hawthorne Blvd., P o r t l a n d 1 4 , O r e g o n Circle No. 8 on Readers' Service Card
INDUSTRIAL AND ENGINEERING CHEMISTRY
(Continued on page 38 Λ)
