Minimizing Nitrosamines Using Sterically Hindered Thiuram Disulfides/Dithiocarbamates

1994 ◽  
Vol 67 (2) ◽  
pp. 299-313 ◽  
Author(s):  
Robert W. Layer ◽  
Dwight W. Chasar
Keyword(s):  
The Other ◽  
Secondary Amines ◽  
Side Reactions ◽  
Other Hand ◽  
Steric Factors ◽  
Sterically Hindered

Abstract Sulfenamide accelerators and sulfur donors based on secondary amines must liberate all of their amine in order to function. Consequently, they are capable of producing relatively large amounts of nitrosamines. Thiuram disulfides and dithiocarbamates, on the other hand, only liberate their amines because of undesired side reactions. Accordingly, compared to sulfenamides, they produce significant, but much lower levels of nitrosamines during the cure. In an effort to reduce these side reactions, and thus the amount of nitrosamine which forms, we investigated the effect of steric factors on nitrosamine formation. We find that thiurams and dithiocarbamates made from sterically bulky amines, like diisobutylamine, produce orders of magnitude lower levels of nitrosamine than TMTD. At the same time, when used as a kicker for 2-benzothiazole sulfenamides, N,N,N′,N′-tetraisobutylthiuram disulfide has better scorch safety but cures at the same rate as TMTD. Uniquely, N,N,N′,N′-tetraisobutylthiuram monosulfide acts as a retarder as well as a kicker for 2-benzothiazole sulfenamides.

Tertiary Alkylative Suzuki-Miyaura couplings

Synthesis ◽  
2022 ◽  
Author(s):  
Takashi Nishikata ◽  
Tom Sheppard ◽  
Naoki Tsuchiya
Keyword(s):  
Oxidative Addition ◽  
Short Review ◽  
The Other ◽  
Side Reactions ◽  
Coupling Reactions ◽  
Other Hand ◽  
Alkyl Electrophiles ◽  
Carbon Bonds ◽  
Beta Hydride Elimination ◽  
Hydride Elimination

The Suzuki-Miyaura coupling is extremely useful to construct Csp2-Csp2 carbon bonds. On the other hand, Csp2-Csp3 coupling reactions are do not work well, and tert-alkylative Suzuki-Miyaura coupling is particularly challenging due to problematic oxidative addition and beta-hydride elimination side reactions. In this short review, we will introduce recent examples of tert-alkylative Suzuki-Miyaura couplings with tert-alkyl electrophiles or -boron reagents. The review will mainly focus on catalyst and product structures and the proposed mechanisms .

Preparation of p-aminobenzyl cellulose and its utilization for immobilization of enzymes

1980 ◽  
Vol 45 (10) ◽  
pp. 2847-2854 ◽  
Author(s):  
Peter Gemeiner ◽  
Ľudovít Kuniak ◽  
Jiří Zemek
Keyword(s):  
Immobilized Enzymes ◽  
The Other ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Other Hand ◽  
Immobilization Of Enzymes ◽  
Molecular Substrates

The O-alkylation of non cross-linked celluloses with p-nitrobenzyl chloride according to Campbell does not afford satisfying results (alkylation degree Da ⪬ 0.025). On the other hand, the use of cross-linked celluloses makes it possible to prepare p-nitrobenzyl cellulose under substantially milder reaction conditions (Da ⪬ 0.42); the degree of cross linking of cellulose considerably affected the Da of p-nitrobenzyl cellulose. The same also holds for O-alkylation of cross-linked celluloses with p-nitrobenzyl chloride according to Hakomori. Reduction of p-nitrobenzyl cellulose with dithionite is considerably associated with side reactions in which sulfur became embodied, whereas reduction with titanous chloride resulted in noticeable losses of p-nitrobenzyl groups. p-Aminobenzyl cellulose is, after activation with carboxyl groups, a suitable carrier for immobilization of enzymes as acetylcholinesterase, glucoamylase and α-amylase. The respective immobilized enzymes retained relatively high relative activities, in the last two cases also for high-molecular substrates.

Photoimaging Materials Based on Base-amplifying Silicone Resins Having Phenylsulfonylethyl Groups

2006 ◽  
Vol 961 ◽  
Author(s):  
Satoru Inoue ◽  
Koji Arimitsu ◽  
Takahiro Gunji ◽  
Yoshimoto Abe ◽  
Kunihiro Ichimura
Keyword(s):  
Uv Curing ◽  
Exposure Dose ◽  
The Other ◽  
Secondary Amines ◽  
Quantum Yields ◽  
Amino Groups ◽  
Other Hand ◽  
Primary Amino ◽  
Secondary Amino ◽  
Catalyzed Reactions

ABSTRACTRecently, the large number of investigations concerning acid-catalyzed photopolymer systems such as chemically amplified photoresists and UV-curing materials has been reported. On the other hand, analogous systems utilizing base-catalyzed reactions have received far less attention, because low quantum yields for photobase generation to lead to low photosensitivity of these systems. To improve this problem, we proposed introduction of the concept of base proliferation reactions into the photopolymer systems using base-catalyzed reactions. The concept involves the autocatalytic base-catalyzed decomposition of a compound, referred to as a base amplifier which releases a newborn amine, leading to its autocatalytic decomposition. In fact, the addition of the base amplifiers such as 9-fluorenylmethyl carbamate, phenylsulfonylethyl carbamate, and 3-nitropentane-2-yl carbamate to a photopolymer consisting of an epoxy polymer sensitized and a photobase generator (PBG) resulted in the marked improvement of photosensitivity.However, these base amplifiers with low molecular weight are not suitable for photopatterning because of the volatility and the excessive diffusion of amines proliferated in polymer films. We report here novel base-amplifying silicone resins tethering phenylsulfonylethyl carbamoyl groups which proliferate primary amino groups or secondary amino groups in their side chains.Base-catalyzed decomposition behavior of films of these resins containing PBG was evaluated by UV absorption measurements. A film consisting of the resin proliferating primary amino groups and 10 wt% of PBG decomposed immediately in a nonlinear manner by 365 nm irradiation and subsequent heat treatment at 120oC for 6 min. On the other hand, this film without UV irradiation was thermally stable for 18 min at 120oC. These results indicate that photoinduced base proliferation reaction of the resin proceeded. A film consisting of the resin generating secondary amino groups and PBG decomposed in a way similar to that of the resin proliferating primary amino groups. Furthermore, lithographic evaluation of the film comprising the resin to generate secondary amines and PBG obtained 7ÊS positive images with an exposure dose of 75 mJ/cm2 which shows higher sensitivity when compared to conventional base-catalyzed photopolymers.

Reactions of Quinolizine- and Pyridino[1,2–a]pyrimidine-3-diazonium Tetrafluoroborates with Aliphatic Amines

2004 ◽  
Vol 59 (4) ◽  
pp. 380-385 ◽  
Author(s):  
Simon Rečnik ◽  
Jurij Svete ◽  
Branko Stanovnik
Keyword(s):  
Picolinic Acid ◽  
The Other ◽  
Aliphatic Amines ◽  
Secondary Amines ◽  
Primary Amines ◽  
Other Hand ◽  
High Yields

KeywordsReactions of 1-cyano-4-oxo-4H-quinolizine-3-diazonium tetrafluoroborate (1a) and 4-oxo-4Hpyridino[ 1,2-a]pyrimidine-3-diazonium tetrafluoroborate (1b) with aliphatic amines 2a - g were studied. Treatment of heteroaryldiazonium salts 1 with secondary amines 2a - d afforded the corresponding N-alkyl-N’-heteroaryltriazenes 3a - h in high yields. On the other hand, reactions of 1a with aliphatic primary amines 2e - g resulted in an unexpected rearrangements into the corresponding picolinic acid N-alkylcarboxamides 4a - c.

β-Acarbose. VII. Approaches Towards the Synthesis of Some N-Linked Carba-Oligosaccharides

1999 ◽  
Vol 52 (9) ◽  
pp. 885 ◽  
Author(s):  
Matthew G. Tilbrook ◽  
Robert V. Stick ◽  
Spencer J. Williams
Keyword(s):  
The Other ◽  
Secondary Amines ◽  
Other Hand ◽  
Glycosyl Donor

3,4-Anhydro-1,6-dideoxy-1,6-episeleno-β-D-glucose was treated with cyclohexylamine to afford an amino diol which was subsequently converted into a cyclic carbamate, a compound shown to be a moderately successful glycosyl donor. Treatment of the same 3,4-anhydro sugar and the 1,6-epithio analogue with a 1-epivalienamine derivative afforded the corresponding secondary amines which were converted into the analogous cyclic carbamates. The epithio analogue was unsuccessful as a glycosyl donor, failing to glycosylate a carbohydrate alcohol. On the other hand, the episeleno compound appeared to function as a glycosyl donor but decomposition of the product occurred under the conditions necessary for its isolation.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

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