A-Bromoisobutyric acid

This synthesis has one rather anomalous application, when a-bromo-isobutyric acid (or its ethyl ester) is heated with silver, some tetramethyl-succinic acid is produced in the ordinary way (B., 23, 297 26, 1458). But there also appears trimethylglutaric acid (A., 292, 220). To explain the unexpected formation of this acid, it has been assumed that a portion of the a-bromoisobutyric acid gives up HBr to form methylacrylic acid. This latter then forms j3-bromoisobutyric acid, and the silver withdraws bromine from the a- and /3 acids, whereby the residues unite to tri-methyl-glutaric acid (B., 22, 48, 60). A similar explanation applies to some other syntheses in which tetramethylsuccinic and trimethylglutaric acids appear together. 

C) Reactivi of the Halogen. For this test use a-bromobutyric, /3-bromobutyric, and a-bromoisobutyric acids. Place 0.1 g or 0.1 ml in separate tubes with 10 ml of water. To each add 1 ml of 0.1 N silver nitrate and observe the extent of reaction after one and after five minutes. 

Bromo-2-metbylpropanoic acid a-Bromoisobutyric acid C4H7Br02 2062-01-9 167.002 cry (peth) 48.6 199 1162< 1.4969"" ... 

In another study, reducible comb-shaped polymers were prepared by using a multifunctional dextran initiator.Dextran modified with an ATRP initiator and disulfide bonds was synthesized by the activation of hydroxyl groups of dextran using GDI followed by its reaction with cystamine (Scheme 3.10). S-S-Dextran was reacted with a-bromoisobutyric acid (BIBA) by EDC/NHS chemistry, and S-S-dextran-Br was then used to polymerize PDMAEMA by ATRP, followed by chain extension with OEGMA, producing a range of copolymers of 10-100 kDa. The comb-shaped copolymers of 86 kDa... 

By cutting off one methylene group in TM 8.4a in retro-Amdt-Eistert mode b, an unfavorable effect of the carbethoxy group in TM 8.4a is inverted by moving this group one bond closer to the carbanion to obtain synthon TM 8.4b. One FGI disconnection leads to TM 8.4c and retro-Grignard to an acceptable reagent derived from a-bromoisobutyric acid. 

Materials. MMA (Sigma-Aldrich)was distilled before use. a- bromoisobutyric acid (98%), isobutyric acid (99 /o), copper bromide I (99,999%), copper bromide 11(99,999%), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HEMA) (97%), 4,4 -dinonyl-2,2 -dipyridyl (dNbpy) (97%), tetrahydrofurane (THF) (99%), methanol (99%), hydrochloric acid (25%), aliguat 336, toluene (99%) were purchased from Sigma-Aldrich and used as received without further purification. 

Functionalization of HAP with ATRP initiator, a- bromoisobutyric acid (9g) was dissolved in deionized water (67,5 ml) and sonicated for 10 minutes. Prepared mixture was placed in round bottom flask with magnetic stir bar and HAP (3g) was added. Reaction was run at 70 C for 24h, next water was evaporated under low pressure. 

Hydroxyapatite modification.Successful attachment of the ATRP initiator was confirmed by elemental analysis. It was possible to tailor the bromine content by changing the concentration of a-bromoisobutyric acid in the reaction mixture used for particles modification. The highest bromine content that was obtained equaled 3,2 10 mmolBr/lg HAP and was reduced to the value of 3,1 10 mmolBr/lg HAP by using 12 times less initiator (0.72g). 

For well-controlled arm number of the star polymers, an efficient approach is the use of multifunctional initiators [157,158]. For instance, the four-armed initiator, NLI-1, which was prepared by the condensation reaction of the hydroxy groups in C(CH20CH2CH2CH20H)4 with a-bromoisobutyric acid, was used in the ATRP of (2,2-dimethyl-l,3-dioxoIane-4-yl)methyl acrylate (DMDMA) with CuBr/bpy as catalyst. After isolation from the polymerization system, four-armed poly(DMDMA)s, such as NLI-2 with Mw/Mn = 1.28—1.41 were obtained, and used in the successive ATRP of MMA, giving star-block copolymers NLB-3. It is known that the cycloacetal ring is unstable in acidic conditions, so the hydrolysis of the block copolymer NLB-3 was accomplished in a 1N HCl aqueous solution to give the amphiphilic star-block copolymer structure NLB-4 as shown in Scheme 3.37 [159]. 

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