title: Hydrogen bonding in hydroxymethylphosphine chalcogenides

authors: Goodwin, Nicholas J.

subjects: Crystal structures

abstract: Hydrogen bonding in the phosphine chalcogenide series Ph2P(X)CH2OH (X=O, 1; S, 2; Se, 3) has been investigated by single crystal X-ray crystallography. While the phosphine oxide exhibits a dimer motif, the sulfide and selenide form infinite chains; in all cases hydrogen bonding is from the OH group to the phosphine chalcogenide heteroatom. The trend in the hydrogen bond angle for OH X-P, which is 117, 87 and 84° for the oxide, sulfide and selenide, respectively, is explained with respect to the geometry of electron density on the phosphine chalcogenide heteroatom.

text: Hydrogen bonding in hydroxymethylphosphine chalcogenides Hydrogen bonding in the phosphine chalcogenide series Ph2P(X)CH2OH (X=O, 1; S, 2; Se, 3) has been investigated by single crystal X-ray crystallography. While the phosphine oxide exhibits a dimer motif, the sulfide and selenide form infinite chains; in all cases hydrogen bonding is from the OH group to the phosphine chalcogenide heteroatom. The trend in the hydrogen bond angle for OH X-P, which is 117, 87 and 84° for the oxide, sulfide and selenide, respectively, is explained with respect to the geometry of electron density on the phosphine chalcogenide heteroatom.

year: 2002-06-01

title: Kinetic studies of redox and related reactions of some new isoalloxazines

authors: Gumbley, Stewart John

abstract: This thesis describes the synthesis of three new isoalloxazines with special structural characteristics which we hoped would, and in fact did, modify their chemical reactivity so as to improve our understanding of mechanisms of flavin reactions generally: kinetic studies of their reactions with a dithiol, reduced nicotinamide and sulphite were made.

A new general synthesis is described for the preparation of o-nitro-(N-alkylamino) aromatic compounds via nucleophilic displacement by alkylamine of a methoxy group ortho to a nitro group. Two new compounds, the isomers 1-(2'-hydroxyethylamino)-2-nitronaphthalene and 2-(2'-hydroxyethylamino)-1-nitronaphthalene, were prepared by this method.

These compounds were used to synthesize two isoalloxazines which each have an additional benzene ring fused either at the 6,7-bond of the isoalloxazine nucleus (7-(2'-hydroxyethyl)-10-methylnaphtho[1,2-g]pteridine- 9,11(7H,10H)-dione; isoalloxazine A) or at the 8,9-bond (12-(2'-hydroxyethyl)-9-methylnaphtho[2,1-g]pteridine- 8,10(9H,12H)-dione; isoalloxazine B). The third new isoalloxazine (10-(2'-hydroxyethyl)-3-methylbenzo[g]pteridine- 2,4(3H,10H)-dione; isoalloxazine C) was prepared by a conventional route.

Kinetic studies, the first recorded for isoalloxazines of the type of A and B, were undertaken for reactions with 1,3-dithio-2-propanol, with NADH and with sulphite.

In the case of the dithiopropanol reaction, a linear free-energy relationship was observed between the logarithm of the second order rate constant and the polarographic half-wave potential, E⅟₂ (slope 26 ± 1 V⁻¹). The conclusion drawn from this is that, if the redox reaction occurs through an addition-elimination sequence, the 5-, 6- and 8-positions are not essential centres for thiol oxidation.

In the case of the reaction with NADH, direct evidence was obtained for the formation of a kinetically important complex between the isoalloxazine and NADH from the observation of saturation kinetics. This is the first reported instance of the observation of such direct evidence for complex formation with NADH. The rate constants for the three isoalloxazines follow the reverse order expected from the E⅟₂ values and from the rates of reaction with DTP. The equilibrium constants (Kₑ) for the complexing of tryptophan with the isoalloxazines were measured by fluorescence quenching. A linear free-energy relationship was not observed between the logarithm of Kₑ and the logarithm of the rate constant for NADH oxidation. It was concluded that the unexpectedly high rate of reaction of A relative to that of B was due to the formation by A of a complex with NADH closer to the hydride acceptor site, the 5-position, than is the case for isoalloxazine B; and that the productivity of the complex therefore is markedly determined by the orientation of the NADH molecule with respect to the isoalloxazine within the complex.

The anaerobic nucleophilic addition reaction of sulphite with isoalloxazines A and C is a two step process of the form X⇌Y→Z, whereas the reaction with B is a single equilibrium step. The reduced isoalloxazine products from A and C are oxidized by molecular oxygen to new isoalloxazines but that from B is not. The new isoalloxazine from C reacts further with sulphite to yield a reduced species different from that of the anaerobic reaction, while the product from A does not react further. These observations provide support for the mechanism previously suggested in the literature for the reaction of sulphite with isoalloxazines. A small rate depression was observed for A relative to B and C in a plot of logarithm of rate constant against E ⅟₂. This is interpreted as being due to steric crowding at the 5-position caused by the α-hydrogen on the naphthalene moiety, an effect not observed in the dithiol reaction which more likely involves nucleophilic addition at the 4a- rather than the 5-position.

text: Kinetic studies of redox and related reactions of some new isoalloxazines This thesis describes the synthesis of three new isoalloxazines with special structural characteristics which we hoped would, and in fact did, modify their chemical reactivity so as to improve our understanding of mechanisms of flavin reactions generally: kinetic studies of their reactions with a dithiol, reduced nicotinamide and sulphite were made.

A new general synthesis is described for the preparation of o-nitro-(N-alkylamino) aromatic compounds via nucleophilic displacement by alkylamine of a methoxy group ortho to a nitro group. Two new compounds, the isomers 1-(2'-hydroxyethylamino)-2-nitronaphthalene and 2-(2'-hydroxyethylamino)-1-nitronaphthalene, were prepared by this method.

These compounds were used to synthesize two isoalloxazines which each have an additional benzene ring fused either at the 6,7-bond of the isoalloxazine nucleus (7-(2'-hydroxyethyl)-10-methylnaphtho[1,2-g]pteridine- 9,11(7H,10H)-dione; isoalloxazine A) or at the 8,9-bond (12-(2'-hydroxyethyl)-9-methylnaphtho[2,1-g]pteridine- 8,10(9H,12H)-dione; isoalloxazine B). The third new isoalloxazine (10-(2'-hydroxyethyl)-3-methylbenzo[g]pteridine- 2,4(3H,10H)-dione; isoalloxazine C) was prepared by a conventional route.

Kinetic studies, the first recorded for isoalloxazines of the type of A and B, were undertaken for reactions with 1,3-dithio-2-propanol, with NADH and with sulphite.

In the case of the dithiopropanol reaction, a linear free-energy relationship was observed between the logarithm of the second order rate constant and the polarographic half-wave potential, E⅟₂ (slope 26 ± 1 V⁻¹). The conclusion drawn from this is that, if the redox reaction occurs through an addition-elimination sequence, the 5-, 6- and 8-positions are not essential centres for thiol oxidation.

In the case of the reaction with NADH, direct evidence was obtained for the formation of a kinetically important complex between the isoalloxazine and NADH from the observation of saturation kinetics. This is the first reported instance of the observation of such direct evidence for complex formation with NADH. The rate constants for the three isoalloxazines follow the reverse order expected from the E⅟₂ values and from the rates of reaction with DTP. The equilibrium constants (Kₑ) for the complexing of tryptophan with the isoalloxazines were measured by fluorescence quenching. A linear free-energy relationship was not observed between the logarithm of Kₑ and the logarithm of the rate constant for NADH oxidation. It was concluded that the unexpectedly high rate of reaction of A relative to that of B was due to the formation by A of a complex with NADH closer to the hydride acceptor site, the 5-position, than is the case for isoalloxazine B; and that the productivity of the complex therefore is markedly determined by the orientation of the NADH molecule with respect to the isoalloxazine within the complex.

The anaerobic nucleophilic addition reaction of sulphite with isoalloxazines A and C is a two step process of the form X⇌Y→Z, whereas the reaction with B is a single equilibrium step. The reduced isoalloxazine products from A and C are oxidized by molecular oxygen to new isoalloxazines but that from B is not. The new isoalloxazine from C reacts further with sulphite to yield a reduced species different from that of the anaerobic reaction, while the product from A does not react further. These observations provide support for the mechanism previously suggested in the literature for the reaction of sulphite with isoalloxazines. A small rate depression was observed for A relative to B and C in a plot of logarithm of rate constant against E ⅟₂. This is interpreted as being due to steric crowding at the 5-position caused by the α-hydrogen on the naphthalene moiety, an effect not observed in the dithiol reaction which more likely involves nucleophilic addition at the 4a- rather than the 5-position.

year: 1976

title: Lavinia and Henry Dunbar Johnson

authors: Hart, Philip

abstract: Rawinia Manukau, of Ngati Tamatera, married Henry Dunbar Johnson in 1868, when aged 21. Johnson had been a storekeeper at Coromandel from 1863 onwards and after 1866 had the first store at the site of the future Paeroa. In both places, but particularly in the latter, there was always the fear of conflict with the local Maori population, despite his being protected by a rangatira. After spending time at the new Thames goldfield, from 1871 onwards he was a partner in another Paeroa store, being able to erect a house because a rangatira related to his wife wished her to settle there. Lavinia (as she was known to Pakeha) obtained interests in several blocks of land in Ohinemuri, and her husband also acquired some land for a farm. He prospected Karangahake mountain from 1866 onwards, despite Maori opposition, and in 1875 and the following year actively mined there, unprofitably; Lavinia was not involved with this field, but did acquire interests in two claims when the Te Aroha one opened.
A petty squabble with a Thames neighbour resulted in Lavinia telling the latter to go back to England – she was feisty in defending her heritage. Through his marriage and close contact with Maori, Johnson understood and admired the Maori language, leading to his being appointed a licensed interpreter in 1872. After being a leading pioneer of Paeroa, in 1879 he went to Wellington to work in the Native Office, leaving his wife and family behind for a while; after then she was employed by Pakeha as a nurse and midwife. 
In 1885 Johnson was appointed to oversee the development of Rotorua, where he attempted to have Maori children educated (as his own were) and had to cope with the aftermath of the 1886 Tarawera eruption. Retrenched in 1888, he farmed for a while on his wife’s land at Te Aroha West, becoming involved in local issues and local politics. During the 1890 he obtained more official positions, and from 1896 to 1906 was a land court judge.
The Johnson family was well integrated into the dominant culture, all his daughters marrying Pakeha apart from one who married a ‘half-caste’ who had been brought up as a Pakeha. Johnson was not a Pakeha Maori in the original sense, but was accepted by Maori when living in Paeroa and as a judge tried to be kind to poverty-stricken Maori, although in time he viewed Maori as becoming lazy compared with those he had lived amongst during his first two decades in New Zealand.

text: Lavinia and Henry Dunbar Johnson Rawinia Manukau, of Ngati Tamatera, married Henry Dunbar Johnson in 1868, when aged 21. Johnson had been a storekeeper at Coromandel from 1863 onwards and after 1866 had the first store at the site of the future Paeroa. In both places, but particularly in the latter, there was always the fear of conflict with the local Maori population, despite his being protected by a rangatira. After spending time at the new Thames goldfield, from 1871 onwards he was a partner in another Paeroa store, being able to erect a house because a rangatira related to his wife wished her to settle there. Lavinia (as she was known to Pakeha) obtained interests in several blocks of land in Ohinemuri, and her husband also acquired some land for a farm. He prospected Karangahake mountain from 1866 onwards, despite Maori opposition, and in 1875 and the following year actively mined there, unprofitably; Lavinia was not involved with this field, but did acquire interests in two claims when the Te Aroha one opened.
A petty squabble with a Thames neighbour resulted in Lavinia telling the latter to go back to England – she was feisty in defending her heritage. Through his marriage and close contact with Maori, Johnson understood and admired the Maori language, leading to his being appointed a licensed interpreter in 1872. After being a leading pioneer of Paeroa, in 1879 he went to Wellington to work in the Native Office, leaving his wife and family behind for a while; after then she was employed by Pakeha as a nurse and midwife. 
In 1885 Johnson was appointed to oversee the development of Rotorua, where he attempted to have Maori children educated (as his own were) and had to cope with the aftermath of the 1886 Tarawera eruption. Retrenched in 1888, he farmed for a while on his wife’s land at Te Aroha West, becoming involved in local issues and local politics. During the 1890 he obtained more official positions, and from 1896 to 1906 was a land court judge.
The Johnson family was well integrated into the dominant culture, all his daughters marrying Pakeha apart from one who married a ‘half-caste’ who had been brought up as a Pakeha. Johnson was not a Pakeha Maori in the original sense, but was accepted by Maori when living in Paeroa and as a judge tried to be kind to poverty-stricken Maori, although in time he viewed Maori as becoming lazy compared with those he had lived amongst during his first two decades in New Zealand.

year: 2016