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Sample records for diaminobiphenyl

  1. Enthalpy/entropy contributions to conformational KIEs: theoretical predictions and comparison with experiment.

    Science.gov (United States)

    Fong, Aaron; Meyer, Matthew P; O'Leary, Daniel J

    2013-02-18

    Previous theoretical studies of Mislow's doubly-bridged biphenyl ketone 1 and dihydrodimethylphenanthrene 2 have determined significant entropic contributions to their normal (1) and inverse (2) conformational kinetic isotope effects (CKIEs). To broaden our investigation, we have used density functional methods to characterize the potential energy surfaces and vibrational frequencies for ground and transition structures of additional systems with measured CKIEs, including [2.2]-metaparacyclophane-d (3), 1,1'-binaphthyl (4), 2,2'-dibromo-[1,1'-biphenyl]-4,4'-dicarboxylic acid (5), and the 2-(N,N,N-trimethyl)-2'-(N,N-dimethyl)-diaminobiphenyl cation (6). We have also computed CKIEs in a number of systems whose experimental CKIEs are unknown. These include analogs of 1 in which the C=O groups have been replaced with CH₂ (7), O (8), and S (9) atoms and ring-expanded variants of 2 containing CH₂ (10), O (11), S (12), or C=O (13) groups. Vibrational entropy contributes to the CKIEs in all of these systems with the exception of cyclophane 3, whose isotope effect is predicted to be purely enthalpic in origin and whose Bigeleisen-Mayer ZPE term is equivalent to DDH‡. There is variable correspondence between these terms in the other molecules studied, thus identifying additional examples of systems in which the Bigeleisen-Mayer formalism does not correlate with DH/DS dissections.

  2. Enthalpy/Entropy Contributions to Conformational KIEs: Theoretical Predictions and Comparison with Experiment

    Directory of Open Access Journals (Sweden)

    Aaron Fong

    2013-02-01

    Full Text Available Previous theoretical studies of Mislow’s doubly-bridged biphenyl ketone 1 and dihydrodimethylphenanthrene 2 have determined significant entropic contributions to their normal (1 and inverse (2 conformational kinetic isotope effects (CKIEs. To broaden our investigation, we have used density functional methods to characterize the potential energy surfaces and vibrational frequencies for ground and transition structures of additional systems with measured CKIEs, including [2.2]-metaparacyclophane-d (3, 1,1'-binaphthyl (4, 2,2'-dibromo-[1,1'-biphenyl]-4,4'-dicarboxylic acid (5, and the 2-(N,N,N-trimethyl-2'-(N,N-dimethyl-diaminobiphenyl cation (6. We have also computed CKIEs in a number of systems whose experimental CKIEs are unknown. These include analogs of 1 in which the C=O groups have been replaced with CH2 (7, O (8, and S (9 atoms and ring-expanded variants of 2 containing CH2 (10, O (11, S (12, or C=O (13 groups. Vibrational entropy contributes to the CKIEs in all of these systems with the exception of cyclophane 3, whose isotope effect is predicted to be purely enthalpic in origin and whose Bigeleisen-Mayer ZPE term is equivalent to ΔΔ H‡. There is variable correspondence between these terms in the other molecules studied, thus identifying additional examples of systems in which the Bigeleisen-Mayer formalism does not correlate with ΔH/ΔS dissections.

  3. Sensitive electrochemical sensing for polycyclic aromatic amines based on a novel core-shell multiwalled carbon nanotubes@ graphene oxide nanoribbons heterostructure.

    Science.gov (United States)

    Zhu, Gangbing; Yi, Yinhui; Han, Zhixiang; Wang, Kun; Wu, Xiangyang

    2014-10-03

    Being awfully harmful to the environment and human health, the qualitative and quantitative determinations of polycyclic aromatic amines (PAAs) are of great significance. In this paper, a novel core-shell heterostructure of multiwalled carbon nanotubes (MWCNTs) as the core and graphene oxide nanoribbons (GONRs) as the shell (MWCNTs@GONRs) was produced from longitudinal partially unzipping of MWCNTs side walls using a simple wet chemical strategy and applied for electrochemical determination of three kinds of PAAs (1-aminopyrene (1-AP), 1-aminonaphthalene and 3,3'-diaminobiphenyl). Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis and electrochemical methods were used to characterize the as-prepared MWCNTs@GONRs. Due to the synergistic effects from MWCNTs and GONRs, the oxidation currents of PAAs at the MWCNTs@GONRs modified glassy carbon (GC) electrode are much higher than that at the MWCNTs/GC, graphene/GC and bare GC electrodes. 1-AP was used as the representative analyte to demonstrate the sensing performance of the MWCNTs@GONRs/GC electrode, and the proposed modified electrode has a linear response range of 8.0-500.0 nM with a detection limit of 1.5 nM towards 1-AP. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Sensitive electrochemical sensing for polycyclic aromatic amines based on a novel core–shell multiwalled carbon nanotubes@ graphene oxide nanoribbons heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Gangbing, E-mail: zhgb1030@ujs.edu.cn [School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013 (China); Yi, Yinhui; Han, Zhixiang [School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013 (China); Wang, Kun [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Wu, Xiangyang, E-mail: wuxy@ujs.edu.cn [School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2014-10-03

    Highlights: • A core–shell heterostructure MWCNTs@GONRs was produced from unzipping MWCNTs. • A new electrochemical sensor for PAAs was developed based on MWCNTs@GONRs hybrids. • The sensor shows good analytical performance for PAAs detection. - Abstract: Being awfully harmful to the environment and human health, the qualitative and quantitative determinations of polycyclic aromatic amines (PAAs) are of great significance. In this paper, a novel core–shell heterostructure of multiwalled carbon nanotubes (MWCNTs) as the core and graphene oxide nanoribbons (GONRs) as the shell (MWCNTs@GONRs) was produced from longitudinal partially unzipping of MWCNTs side walls using a simple wet chemical strategy and applied for electrochemical determination of three kinds of PAAs (1-aminopyrene (1-AP), 1-aminonaphthalene and 3,3′-diaminobiphenyl). Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis and electrochemical methods were used to characterize the as-prepared MWCNTs@GONRs. Due to the synergistic effects from MWCNTs and GONRs, the oxidation currents of PAAs at the MWCNTs@GONRs modified glassy carbon (GC) electrode are much higher than that at the MWCNTs/GC, graphene/GC and bare GC electrodes. 1-AP was used as the representative analyte to demonstrate the sensing performance of the MWCNTs@GONRs/GC electrode, and the proposed modified electrode has a linear response range of 8.0–500.0 nM with a detection limit of 1.5 nM towards 1-AP.

  5. Sensitive electrochemical sensing for polycyclic aromatic amines based on a novel core–shell multiwalled carbon nanotubes@ graphene oxide nanoribbons heterostructure

    International Nuclear Information System (INIS)

    Zhu, Gangbing; Yi, Yinhui; Han, Zhixiang; Wang, Kun; Wu, Xiangyang

    2014-01-01

    Highlights: • A core–shell heterostructure MWCNTs@GONRs was produced from unzipping MWCNTs. • A new electrochemical sensor for PAAs was developed based on MWCNTs@GONRs hybrids. • The sensor shows good analytical performance for PAAs detection. - Abstract: Being awfully harmful to the environment and human health, the qualitative and quantitative determinations of polycyclic aromatic amines (PAAs) are of great significance. In this paper, a novel core–shell heterostructure of multiwalled carbon nanotubes (MWCNTs) as the core and graphene oxide nanoribbons (GONRs) as the shell (MWCNTs@GONRs) was produced from longitudinal partially unzipping of MWCNTs side walls using a simple wet chemical strategy and applied for electrochemical determination of three kinds of PAAs (1-aminopyrene (1-AP), 1-aminonaphthalene and 3,3′-diaminobiphenyl). Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis and electrochemical methods were used to characterize the as-prepared MWCNTs@GONRs. Due to the synergistic effects from MWCNTs and GONRs, the oxidation currents of PAAs at the MWCNTs@GONRs modified glassy carbon (GC) electrode are much higher than that at the MWCNTs/GC, graphene/GC and bare GC electrodes. 1-AP was used as the representative analyte to demonstrate the sensing performance of the MWCNTs@GONRs/GC electrode, and the proposed modified electrode has a linear response range of 8.0–500.0 nM with a detection limit of 1.5 nM towards 1-AP

  6. Low dielectric constant and moisture-resistant polyimide aerogels containing trifluoromethyl pendent groups

    Science.gov (United States)

    Wu, Tingting; Dong, Jie; Gan, Feng; Fang, Yuting; Zhao, Xin; Zhang, Qinghua

    2018-05-01

    Conventional polyimide aerogels made from biphenyl-3,3‧,4,4‧-tetracarboxylic dianydride (BPDA) and 4,4‧-oxidianiline (ODA) exhibit poor resistance to moisture and mechanical properties. In this work, a versatile diamine, 2,2‧-bis-(trifluoromethyl)-4,4‧-diaminobiphenyl (TFMB), is introduced to BPDA/ODA backbone to modify the comprehensive performance of this aerogel. Among all formulations, the resulted polyimide aerogels exhibit the lowest shrinkage and density as well as highest porosity, at the ODA/TFMB molar ratio of 5/5. Dielectric constants and loss tangents of the aerogels fall in the range of 1.29-1.33 and 0.001-0.004, respectively, and more TFMB fractions results in a slightly decrease of dielectric constant and loss tangent. In addition, moisture-resistance of the aerogels are dramatically enhanced as the water absorption decreasing from 415% for BPDA/ODA to 13% for the polyimide aerogel at the ODA/TFMB molar ratio of 7/3, and even to 4% for the homo-BPDA/TFMB polyimide aerogel, showing a superhydrophobic characteristic, which is a great advantage for polyimide aerogels used as low dielectric materials. Meanwhile, all of formulations of aerogels exhibit high absorption capacities for oils and common organic solvents, indicating that these fluorinated polyimide aerogels are good candidates for the separation of oils/organic solvents and water. Mechanical properties and thermal stability of the polyimide aerogels are also raised to varying degrees due to the rigid-rod biphenyl structure introduced by TFMB.

  7. NTP Toxicology and Carcinogenesis Studies of 3,3'-Dimethoxybenzidine Dihydrochloride (CAS No. 20325-40-0) in F344/N Rats (Drinking Water Studies).

    Science.gov (United States)

    1990-01-01

    . 3,3'-Dimethoxybenzidine did not induce sex-linked recessive lethal mutations in adult male D. melanogaster exposed via feeding or injection. Conclusions: Under the conditions of these 21-month drinking water studies, there was clear evidence of carcinogenic activity of 3,3'-dimethoxybenzidine dihydrochloride for male F344/N rats, as indicated by benign and malignant neoplasms of the skin, Zymbal gland, preputial gland, oral cavity, intestine, liver, and mesothelium. Increased incidences of astrocytomas of the brain may have been related to chemical administration. There was clear evidence of carcinogenic activity of 3,3'-dimethoxybenzidine dihydrochloride for female F344/N rats, as indicated by benign and malignant neoplasms of the Zymbal gland, clitoral gland, and mammary gland. Increases in neoplasms of the skin, oral cavity, large intestine, liver, and uterus/cervix were also considered to be related to chemical administration of 3,3'-dimethoxybenzidine dihydrochloride. Synonyms: o-dianisidine dihydrochloride; 3,3'-dimethoxy-1,1-biphenyl)-4,4'-diamine dihydrochloride; 3,3'-dimethoxy-4,4'-diaminobiphenyl dihydrochloride