Acceleration of Specific Reactions of Amines with Nitrite in Ice

概要

Acceleration of Specific Reactions of Amines
with Nitrite in Ice
著者
内容記述
URL

北田 耕大
学位記番号：論工第1591号, 指導教員：竹中 規訓
http://doi.org/10.24729/00017210

Acceleration of Specific Reactions of Amines with
Nitrite in Ice

（氷中におけるアミン類と亜硝酸の
特異的な反応の促進）

Kodai Kitada

北

田

耕

大

February 2020

Doctral Thesis at Osaka Prefecture University

Table of Contents
Chapter 1 Introduction and Background ..................................................................... 1
Chapter 2 Acceleration and Reaction Mechanism of N-Nitrosation Reaction of
Dimethylamine with Nitrite in Ice ............................................................................... 13
2.1 Introduction ......................................................................................................... 13
2.2 Experimental ....................................................................................................... 16
2.3 Results and discussions ....................................................................................... 17
2.3.1 N-Nitrosation in Ice ........................................................................................ 17
2.3.2 Reaction Order for N-Nitrosation ................................................................... 20
2.3.3 Partition Coefficients to Ice ............................................................................ 24
2.4 Conclusion............................................................................................................ 26
Chapter 3 Cyanide Formation in Freezer-Stored Foods - Freezing of a Glycine and
Nitrite Mixture .............................................................................................................. 34
3.1 Introduction ......................................................................................................... 34
3.2 Experimental ....................................................................................................... 35
3.3 Results and Discussions ...................................................................................... 37
3.3.1 Formation of Cyanide ..................................................................................... 37
3.3.2 pH Dependence of Cyanide Formation .......................................................... 38
3.3.3 Reactivities of the C-nitrosation Reactions .................................................... 45
3.3.4 Effect of Ascorbic Acid Addition ................................................................... 48
3.4 Conclusion............................................................................................................ 50

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Chapter 4 The Effect of Freezing on Ammonium Concentration Resulting from
Reaction of Urea with Nitrite ...................................................................................... 56
4.1 Introduction ......................................................................................................... 56
4.2 Experimental ....................................................................................................... 57
4.3 Results and discussions ....................................................................................... 58
4.3.1 pH Dependence of N-Nitrosation of Urea ...................................................... 58
4.3.2 Effect of Urea /Nitrite Ratio ........................................................................... 60
4.3.3 The Effect of Freezing Temperature ............................................................... 62
4.4 Conclusion............................................................................................................ 63
Chapter 5 Conclusion and Future Research .............................................................. 69
List of publications ....................................................................................................... 71
Acknowledgement ......................................................................................................... 73

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Chapter 1 Introduction and Background
Since ancient time, people have preserved foods in a place at low temperature, like
ice house. People have empirically known that chemical and biochemical reactions are
suppressed at lower temperature. In fact, almost all chemical reactions slow down at lower
temperatures. After the refrigerator was developed in the 19th century, it gained
widespread use all over the world. In the 20th century of japan, refrigerators, along with
televisions and washing machines, were called three sacred treasures, “sansyu no jingi”.
The ability to easily store foods at home has changed people's lives significantly.
Freezers have also changed the lives of people. The advent of freezers has made it
possible to store food for a much longer time than refrigerators. Now, frozen foods that
can be eaten immediately when heated in a microwave oven are displayed in supermarkets
and convenience stores. While these inventions enriched people's lives, nutritional
imbalance and additives in frozen foods became a problem. However, the general public
and even scientists did not think that freezing would promote certain chemical reactions.
In 1992, Takenaka et al. reported that the rate of oxidation reaction of nitrite ion was
200,000 times faster under the freezing condition at -20 ℃ than that in solution at
4 ℃.1 Various considerations have been made for this reason. The reaction was not
promoted even when the ice made of pure water was put into the system; therefore, it
was not a catalytic reaction on the ice surface. Since no change in reactivity was observed
with or without room light, it was not a photocatalytic reaction. In addition, the reaction
was not promoted even when the solution was stirred and was frozen to form single
crystal ice, and the reaction is promoted only in polycrystalline ice. When ice and
unfrozen solution in freezing solution from the bottom were separated, nitrate produced

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through this reaction was found only in ice phase. Furthermore, the reaction is not
promoted unless the reaction order is second or higher. The reaction rate depends on the
temperature and the concentration, but the reaction rate increases even when the
temperature is lowered. From the above, it was concluded that the reaction promoted by
freezing was explained by freeze concentration.
When ice grows, at the beginning, a lot of small ices are generated and solution around
polycrystalline ices is concentrated. This is because little amount of solute is taken into
ice crystals. Concentration in unfrozen solution confined by polycrystalline ice crystals
increases gradually over time. Finally, reaction proceeds in extremely concentrated
unfrozen solution in ice. A chain of this phenomenon causes acceleration of reaction in
ice. This mechanism is shown in Figure 1-1.8

Figure 1-1 Illustrative elucidation of acceleration mechanism by freezing. Only five
single ice crystals are depicted for simplicity. I, single crystal of ice; C,
concentrated phase; S, solution confined in the solution surrounded by walls
of ice grains; R, concentrated solution in which the reaction is accelerated.

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However, we cannot explain all reactions in ice only through this phenomenon. A
variety of phenomena occur in unfrozen solutions in ice. Although little amount of solute
is taken in ice crystals, unfrozen solution in ice is significantly affected by the trace
transfer of solute from solution to ice and vice versa. The amount of solute taken into ice
depends on kind of solutes.2-4 pH of the unfrozen solution in ice is affected by this
difference. pH change is very important factor for many chemical reactions. Under
freezing condition, oxidation of gallic acid by dissolved oxygen occurs only in alkaline
solution but not in neutral or acidic solution. However, it is promoted also in neutral or
acidic solution by freezing when sodium chloride is added.5 When solution of sodium
chloride freezes, more chloride ion is taken into ice than sodium ion. Chloride ion takes
more hydronium ion than sodium ion to ice to cancel electrical charge. This causes the
increase of concentration of hydroxide ion and increase of pH in the unfrozen solution.
The difference of the amount of solute taken into ice generates an electric potential
between ice and solution.6-8 This potential also may be a motivation of electrochemical
reaction.
Some reactions behave in different way in ice against in solution. UV photolysis
(>280 nm) of monochlorophenols leads to efficient coupling reactions in ice and
photosolvolysis products in liquid water due to decrease of free water molecules.9 Other
reactions are proceeded by ice work as catalyst. Ozonation of diphenylethylene(DPE)
proceeds at lower temperature on the surface of ice grains produced by shock-freezing of
DPE aqueous solutions or DPE vapor-deposition on pure ice grains.10 Quasi-liquid layer
exists around the surface of ice at relatively high subzero temperature. At lower subzero
temperature, this layer decreases and surface area that ozone can be absorbed increase.
This caused ozonation of DPE.

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Although various phenomena occur in ice, many reactions promoted by freeze
concentration have been reported since 1992.11-18 In 2011, Takenaka et al. reported that
the denitrification of ammonium nitrite was accelerated by freeze concentration under
acidic condition.19 In this reaction, the pH at which the maximum reaction rate observed
at different pHs in solution and freezing (the pH under freezing conditions means the pH
of the solution before freezing). They explained that the cause is that the pH dropped due
to an increase in the hydronium ion concentration due to freeze concentration. This
reaction starts from N-nitrosation of ammonium ion with nitrite ion. The N-nitrosation
reaction is a reaction in which amines and nitrite ions react secondary or tertiary under
acidic conditions to produce nitrosamines. ...

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