Science Record

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neglected if the glycol contains more than five carbon atoms in the chain (in the diethylene glycol there are four carbon atoms and one oxygen atom). Hence, we may predict that the velocity constants of polyesterification reactions between dibasic acids and glycols in which two hydroxyl groups at the end of the chain have more than six carbon atoms reach a limiting value of the velocity constants of the polyesterification reactions. From the above discussions we may conclude that the fundamental assumption in the polyesterification, i.., that all the similar functional groups in the reaction having the same reactivity and hence the same velocity constant independent of the length of the carbon atoms in the chain, represents rather truely the actual condition.

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15)

K-10

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05

0 { J ‘3 L = chs . — ers — 3) Asi ve Te OE SE OG Ge Number of carbon atoms in the dibasic acids.

Fig. 6 Relationships between the velocity constants and the molecular structures of dibasic acids and glycols. : 1—ethylene glycol; 2—4, 2-propylene glycol; 3 — diethylene glycol; 4—1, 4-butylene glycol; 5'— 16-hexamethylene glycol.