Thermal decomposition of propargyl alcohol: single pulse shock tube experimental and ab initio theoretical study.

Thermal decomposition of propargyl alcohol (C3H3OH), a molecule of interest in interstellar chemistry and combustion, was investigated using a single pulse shock tube in the temperature ranging from 953 to 1262 K. The products identified include acetylene, propyne, vinylacetylene, propynal, propenal, and benzene. The experimentally observed overall rate constant for thermal decomposition of propargyl alcohol was found to be k = 10((10.17 ± 0.36)) exp(-(39.70 ± 1.83)/RT) s(-1). Ab initio theoretical calculations were carried out to understand the potential energy surfaces involved in the primary and secondary steps of propargyl alcohol thermal decomposition. Transition state theory was used to predict the rate constants, which were then used and refined in a kinetic simulation of the product profile. The first step in the decomposition is C-O bond dissociation, leading to the formation of two important radicals in combustion, OH and propargyl. This has been used to study the reverse OH + propargyl radical reaction, about which there appears to be no prior work. Depending on the site of attack, this reaction leads to propargyl alcohol or propenal, one of the major products at temperatures below 1200 K. A detailed mechanism has been derived to explain all the observed products.

Synthesis and biological evaluation of new Tetra-aza macrocyclic scaffold constrained oxadiazole, thiadiazole and triazole rings.

A new series of N,N'-(benzene-1,3-diyldi-1,3,4-oxadiazole-5,2-diyl)bis{2-[(5-benzene-1,3-diyl-1,3,4-oxadiazol-2-yl)amino]acetamide}(macrocycle 1), N,N'-(benzene-1,3-diyldi-1,3,4-thiadiazole-5,2-diyl)bis{2-[(5-benzene-1,3-diyl-1,3,4-thiadiazol-2-yl)amino]acetamide} (macrocycle 2) and S,S'-[benzene-1,3-diylbis(4H-1,2,4-triazole-5,3-diyl)]bis{[(5-benzene-1,3-diyl-4H-1,2,4-triazol-3-yl)sulfanyl]ethanethioate}(macrocycle 3) was synthesized from isophthalic dihydrazide (4) through a multistep reaction sequence. All the synthesized compounds were screened for their inhibitory effect against four different bacterial strains: P. aeruginosa ATCC-20852, K. pneumoniae MTCC-618, S. aureus ATCC- 29737, S. typhi MTCC- 3214. The synthesized compounds showed a significant zone of inhibition and the results were comparable with that of the standard drug ciprofloxacin. The synthesized compounds were further studied for their possible in vitro antioxidant effects by DPPH scavenging, total antioxidant capacity, total reductive capacity and H(2) O(2) scavenging activity. The results indicated that the in vitro antioxidant activity for all the three molecules was efficient when compared to the standards. The DNA interaction behavior of macrocycles 1-3 with CT-DNA was investigated by the absorption spectra obtained (K(b) constant for 1 is 4.53 × 10(4) M(-1) , for 2 is 5.75 × 10(4) M(-1) and for 3 is 5.86 × 10(4) M(-1) ). Based on the results it can be interpreted that the reducing power effect of the newly synthesized compounds demonstrates a direct effect on DNA binding and hence inhibiting the bacterial growth through their action on DNA by inhibiting DNA replication or DNA transcription.

Synthesis, DNA binding, and photonuclease activity of new tetraaza macrocyclic constrained isoxazole rings as subunit in metal complexes.

The DNA-binding and photonuclease activity of newly synthesized tetra-azamacrocyclic ligand L (C(32)H(32)N(8)O(4)) and its complexes of type [MLCl(2)] and [ML]Cl(2) (where M = Co(II), Fe(II) and Cu(II); L = N,N'-[3-(4-{5-[(2-amino-ethylamino)-methyl]-isoxazol-3yl}-phenyl)-isoxazol-5-yl methyl-ethane-1,2-diamine] are specified. An octahedral geometry has been proposed for Fe(II) and Co(II) complexes, while the Cu(II) complex has a square planar environment. The absorption spectral results indicate that the complexes bind with the base pairs of DNA, with an intrinsic binding constant K(b) of Fe(II), Co(II), and Cu(II) complexes found to be 3.2 × 10(4) M(-1), 5.3 × 10(4) M(-1), and 4.2 × 10(4) M(-1), respectively, in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2. The large enhancement in the relative viscosity of DNA on binding to the complexes supports the proposed DNA binding modes. The viscosity and thermal denaturation studies sustain the effective intercalation with DNA. The DNA photocleavage studies demonstrated that compounds exhibit significant photonuclease activity by a concentration dependent on singlet oxygen mediated mechanism.

Synthesis, DNA-binding, DNA-photonuclease profiling and antimicrobial activity of novel tetra-aza macrocyclic Ni(II), Co(II) and Cu(II) complexes constrained by thiadiazole.

A new tetra-aza macrocyclic ligand, L (C(24)H(16)N(12)O(2)S(4)) and its complexes of type, [MLCl(2)] and [CuL]Cl(2) (where M=Ni(II), Co(II); L=N,N'-(benzene-1,3-diyldi-1,3,4-thiadiazole-5,2-diyl)bis{2-[(5-benzene-1,3-diyl-1,3,4-thiadiazol-2-yl)amino]acetamide}) were synthesized and characterized by the spectral and analytical techniques. An octahedral geometry has been proposed for Ni(II) and Co(II) complexes while Cu(II) complex exhibit a square planar geometry. All the synthesized metal complexes were screened for their in vitro antimicrobial activity against selected species of pathogenic bacteria and fungi. The binding property of the complexes with CT-DNA was studied by absorption spectral analysis, followed by viscosity measurement and thermal denaturation studies. The photo induced cleavage studies revealed that the complexes possess photonuclease property against pUC19 DNA under UV-visible irradiation.

Synthesis, DNA binding, and oxidative cleavage studies of Fe(II) and Co(III) complexes containing bioactive ligands.

The two complexes containing bioactive ligands of the type and [Fe(L)] (PF(6))(2) (1) (where L = [1-{[2-{[2-hydroxynaphthalen-1-yl)methylidine]amino}phenyl)imino] methyl}naphthalene-2-ol]) and [Co(L(1)L(2))] (PF(6))(3) (2) (where L(1)L(2) = mixed ligand of 2-seleno-4-methylquinoline and 1,10-phenanthroline in the ratio 1:2, respectively) were synthesized and structurally characterized. The DNA binding property of the complexes with calf thymus DNA has been investigated using absorption spectra, viscosity measurements, and thermal denaturation experiments. Intrinsic binding constant K(b) has been estimated at room temperature. The absorption spectral studies indicate that the complexes intercalate between the base pairs of the CT-DNA tightly with intrinsic DNA binding constant of 2.8 × 10(5) M(-1) for (1) and 4.8 × 10(5) M(-1) for (2) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2, respectively. The oxidative cleavage activity of (1) and (2) were studied by using gel electrophoresis and the results show that complexes have potent nuclease activity.

Scrub typhus presenting as acute abdomen.

Scrub typhus, a zoonosis, is a systemic febrile illness with diverse clinical manifestations. It may also present with signs and symptoms of acute abdomen. We present two serologically confirmed cases of scrub typhus presenting with acute abdomen that were managed conservatively with antibiotics.