ATRP of Methyl Acrylate by Continuous Feeding of Activators Giving Polymers with Predictable End-Group Fidelity

Atom transfer radical polymerization (ATRP) of methyl acrylate (MA) was carried out by continuous feeding of Cu(I) activators. Typically, the solvent, the monomer, the initiator, and the CuBr2/Me6TREN deactivator are placed in a Schlenk flask (Me6TREN: tris[2-(dimethylamino)ethyl]amine), while the CuBr/Me6TREN activator is placed in a gas-tight syringe and added to the reaction mixture at a constant addition rate by using a syringe pump. As expected, the polymerization started when Cu(I) was added and stopped when the addition was completed, and polymers with a narrow molecular weight distribution were obtained. The polymerization rate could be easily adjusted by changing the activator feeding rate. More importantly, the loss of chain end-groups could be precisely predicted since each loss of Br from the chain end resulted in the irreversible oxidation of one Cu(I) to Cu(II). The Cu(I) added to the reaction system may undergo many oxidation/reduction cycles in ATRP equilibrium, but would finally be oxidized to Cu(II) irreversibly. Thus, the loss of chain end-groups simply equals the total amount of Cu(I) added. This technique provides a neat way to synthesize functional polymers with known end-group fidelity.

Confounding contaminants in mass spectrometric reaction monitoring

<p>Reactions carried out in the presence of rubber septa run the risk of additives being leached out by the solvent. Normally, such species are present at low enough levels that they do not interfere with the reaction significantly. However, when studying reactions using sensitive methods such as mass spectrometry, the appearance of even trace amounts of material can confuse dynamic analyses of reactions. A wide variety of additives are present in rubber along with the polymer: antioxidants, dyes, detergent, and vulcanization agents, and these are all especially problematic in negative ion mode. A redesigned Schlenk flask for pressurized sample infusion (PSI) is presented as a means of practically eliminating the presence of contaminants during reaction analyses.</p>

Confounding contaminants in mass spectrometric reaction monitoring

<p>Reactions carried out in the presence of rubber septa run the risk of additives being leached out by the solvent. Normally, such species are present at low enough levels that they do not interfere with the reaction significantly. However, when studying reactions using sensitive methods such as mass spectrometry, the appearance of even trace amounts of material can confuse dynamic analyses of reactions. A wide variety of additives are present in rubber along with the polymer: antioxidants, dyes, detergent, and vulcanization agents, and these are all especially problematic in negative ion mode. A redesigned Schlenk flask for pressurized sample infusion (PSI) is presented as a means of practically eliminating the presence of contaminants during reaction analyses.</p>

Confounding contaminants in mass spectrometric reaction monitoring

<p>Reactions carried out in the presence of rubber septa run the risk of additives being leached out by the solvent. Normally, such species are present at low enough levels that they do not interfere with the reaction significantly. However, when studying reactions using sensitive methods such as mass spectrometry, the appearance of even trace amounts of material can confuse dynamic analyses of reactions. A wide variety of additives are present in rubber along with the polymer: antioxidants, dyes, detergent, and vulcanization agents, and these are all especially problematic in negative ion mode. A redesigned Schlenk flask for pressurized sample infusion (PSI) is presented as a means of practically eliminating the presence of contaminants during reaction analyses.</p>

Synthesis and X-ray diffraction data of 4-benzyloxy-1-oxaspiro-[4.6]-undec-3-en-2-one

The 4-benzyloxy-1-oxaspiro-[4.6]-undec-3-en-2-one (C17H20O3) was prepared through a domino reaction from benzyl α-hydroxycycloheptanecarboxylate and the cumulated ylide Ph3P=C=C=O by: (i) addition and (ii) intramolecular Wittig Olefination reaction. The reaction was carried out using anhydrous toluene as solvent under an argon atmosphere in a Schlenk flask. Molecular characterization was performed by Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, (1H,13C – mono and bidimensional) nuclear magnetic resonance spectroscopy; crystallographic characterization was completed by X-ray diffraction of polycrystalline samples (XRPD). The title compound crystallized in a monoclinical system and unit-cell parameters are reported [a = 13.207(3) Å, b = 5.972(1) Å, c = 19.719(4) Å, β = 105.67(2)°, unit-cell volume V = 1497.5 (4) Å3, Z = 4]. All of the measured lines were indexed with the P21/n (No. 14) space group.