Initiation reaction propylene oxide addition

Polyether Polyols. Polyether polyols are addition products derived from cyclic ethers (Table 4). The alkylene oxide polymerisation is usually initiated by alkah hydroxides, especially potassium hydroxide. In the base-catalysed polymerisation of propylene oxide, some rearrangement occurs to give aHyl alcohol. Further reaction of aHyl alcohol with propylene oxide produces a monofunctional alcohol. Therefore, polyether polyols derived from propylene oxide are not truly diftmctional. By using sine hexacyano cobaltate as catalyst, a more diftmctional polyol is obtained (20). Olin has introduced the diftmctional polyether polyols under the trade name POLY-L. Trichlorobutylene oxide-derived polyether polyols are useful as reactive fire retardants. Poly(tetramethylene glycol) (PTMG) is produced in the acid-catalysed homopolymerisation of tetrahydrofuran. Copolymers derived from tetrahydrofuran and ethylene oxide are also produced. 

Block copolymers of /3-PL and /3-BL have been synthesized using (251), although reaction times of several weeks are required.782 Since (TPP)Al-based carboxylates are also known to polymerize epoxides (see Section 9.1.7.2), the sequential addition of /3-BL and propylene oxide (PO) results in formation of a p(/3-BL-/3-PO) diblock.782 However, reversing the order of addition fails to produce the block copolymer since the propagating alkoxide (TPP)Al(OCHMeCH2)nCl does not initiate the ROP of /3-BL. 

Carbocation-oxonium ion equilibria are obvious complicating factors in studies of the kinetics of initiation of polymerisation and useful thermodynamic data for such equilibria involving Ph3C+ and a variety of linear and cyclic ethers have been reported by Slomkowski and Penczek (132). A dramatic increase in rates of initiation of polymerisation of THF induced by Ph3C+ salts is observed on addition of small amounts of epoxides such as propylene oxide (113a,b), which compete favourably with THF in the primary carbocation-oxonium ion equilibria and simplify the initiation reaction ... 

To explain their results, Daniel and Keulks proposed that allyl hydroperoxide (or peroxide) was the initiator of the gas-phase reaction since hydroperoxides are known to be good radical reaction initiators. In addition, it was felt that the decomposition of allyl hydroperoxide in the gas phase could result in the formation of propylene oxide and even acrolein. They proposed a modified reaction mechanism, which is presented in Fig. 3. 

As shown in Scheme 9, various organic compounds can act as a chiral initiator of asymmetric auto catalysis. 2-Methylpyrimidine-5-carbaldehyde 9 was subjected to the addition of z-Pr2Zn in the presence of chiral butan-2-ol, methyl mandelate and a carboxylic acid [74], When the chiral alcohol, (S)-butan-2-ol with ca. 0.1% ee was used as a chiral initiator of asymmetric autocatalysis, (S)-pyrimidyl alkanol 10 with 73% ee was obtained. In contrast, (,R)-butan-2-ol with 0.1% ee induced the production of (A)-10 with 76% ee. In the same manner, methyl mandelate (ca. 0.05% ee) and a chiral carboxylic acid (ca. 0.1% ee) can act as a chiral initiator of asymmetric autocatalysis, therefore the S- and IC enantiomers of methyl mandelate and carboxylic acid induce the formation of (R)- and (S)-alkanol 10, respectively. Chiral propylene oxide (2% ee) and styrene oxide (2% ee) also induce the imbalance of ee in initially forming the zinc alkoxide of the pyrimidyl alkanol in the addition reaction of z-Pr2Zn to pyrimidine-5-carbaldehyde 11 [75]. Further consecutive reactions enable the amplification of ee to produce the highly enantiomerically enriched alkanol 12 (up to 96% ee) with the corresponding... 

Stable trityl salts, which might lead to systems devoid of side reactions, do not however initiate polymerization of the majority of heterocyclic monomers by direct addition The only reported exception is the copolymerization of THF with propylene oxide ... 

Addition of ethylene oxide and propylene oxide to fatty amines prepared from naturally occurring fatty acids encounters no difficulties. The reaction results in surfactants of mainly nonionic character those are characterised by better compatibility with anionics and moderate toxicity in comparison to initial amines. The ethoxylated fatty amines found application in textile finishing, acidic cleaners and cosmetics. Commercial ethoxylated fatty amines are known, for example, as Ethomeen , Genamin C/O/S/T , Imbentin-CAM/OTM , Marlazin , and Rhodameen/Cemulcat series of Akzo Nobel, Clariant, Kolb, Condea, and Rhodia, respectively. 

Block copolymers consisting of segments with widely separated solubility characteristics have generated considerable interest because of their unusual surfactant properties. In fact, one of the earliest commercial block copolymers were the Wyandotte "Pluronics." These were poly(propylene oxide-b-ethylene oxide) prepared by sequential addition of ethylene oxide to sodium alkoxide initiated propylene oxide (37,38). Szwarc (39) and others (40,41) prepared poly(styrene-b-ethylene oxide) by addition of ethylene oxide to polystyrene anions in tetrahydrofuran. Other syntheses of AB or ABA block copolymers of styrene-ethylene oxide include sequential addition in various solvents, and coupling reactions (42,43). 

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