Citric Acid

365 Pages·2014·18.12 MB·English

by  Alexander Apelblat (auth.)

CITRIC ACID
Alexander Apelblat
CITRIC ACID
1 3
Alexander Apelblat
Department of Chemical Engineering
Ben-Gurion University of the Negev
Beer Sheva
Israel

ISBN 978-3-319-11232-9 ISBN 978-3-319-11233-6 (eBook)
DOI 10.1007/978-3-319-11233-6
Springer Cham Heidelberg New York Dordrecht London
Library of Congress Control Number: 2014955173
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To Ira and Yoram
Preface
Substantial part of my scientific activity was devoted to physicochemical properties
of aqueous solutions of citric acid and various inorganic citrates. They included for-
mation of metal-mixed complexes, determinations of solubilities, vapour pressures
of water above citric acid and citrates solutions, densities, melting points, sound
velocities and electrical conductances. Unquestionably, the industrial and biologi-
cal importance of citric acid was the main motivation that more than 25 scientific
papers I published together with my coworkers on systems with citrate ions. Our
results up to 1994, I summarized in the review entitled “Thermodynamic and Trans-
port Properties of Aqueous Solutions of Hydroxycarboxylic Acids.” The current
book came as a desire to enlarge the information about citric acid properties pre-
sented there, to incorporate some subjects which were entirely omitted (chemistry
of citric acid and properties of inorganic citrate solutions) and finally to include our
and others new relevant results.
My interests in citric acid grew especially after I measured and interpreted electri-
cal conductances of citric acid in aqueous solutions. This actually introduced me for
the first time to electrochemistry of unsymmetrical electrolytes, the subject which
even today, continue to be an important part of my scientific activity. The idea to
write a book about citric acid came also from desire to be involved in something
which is applicable oriented. This came from the fact that when I started studying
chemical engineering my Father said to me that he expects that I will be successful
in “practical chemistry”. His intention was clear, that my work will finally lead to a
some useful patent. He was satisfied with my career as a chemical engineer, math-
ematician and physical chemist, but I think in spite that he never said this, he was a
little disappointed. In my professional life I meet a number of very interesting and
important scientific and engineering problems to solve, but they never resulted in a
product finishing on the market. So, writing about citric acid, which evidently is a
huge commodity, is in a some way fulfilling his desire that I will be more practical
in my work. However, this is once again only partially satisfied, because the pres-
ent book is mainly devoted to physicochemical properties of solutions and not to
engineering and technological aspects of citric acid production or its biological role.
These subjects are only marginally treated and the enormous fields of formation of
citrate complexes and chemical analysis in systems with citrate ions are also nearly
omitted. Nevertheless, I believe that included in this book information, also a very
vii
viii Preface
extensive list of references on different aspects dealing with citric acid will be of
interest and help not only to people involved with the basic research of systems with
citric ions, but also to those who are engaged with its production and use. Thus,
there is an intention that this book will serve graduate students and researchers in
various domains of chemistry, biotechnology, biochemistry and biology who are
studying properties, chemical reactions and applications of hydroxycarboxylic ac-
ids, but also engineers who are producing them. Evidently, it is my expectation that
that the present book will stimulate further research on chemistry and properties of
citric acid and compounds related to it. The book consists of five Chapters, each
devoted to different aspects associated with citric acid.
Chapter 1 includes general information about properties, occurrence, importance
in living organisms and technological applications of citric acid. It contains also a
short history linked with the discovery and development of citric acid production.
It lists also most important physicochemical investigations dealing with citric acid
solutions.
Chapter 2 is devoted to properties of solid citric acid and aqueous and organic
solutions of it. Detailed phase equilibria in the citric acid + water system (melting,
freezing, boiling, solubilities and vapour pressures curves) are presented, correlated
and thermodynamically analyzed. Dynamic and other physical properties (viscosi-
ties, diffusion coefficients, thermal and electrical conductivities, surface tensions
and indices of refraction) are examined. Solubilities of citric acid in organic sol-
vents and ternary citric acid + aliphatic alcohol + water and citric acid + tertiary
amine + water systems are also discussed.
Chapter 3 is dedicated to comprehensive presentation of mathematical proce-
dures associated with dissociation of citric acid in water and in electrolyte solutions.
Available in the literature dissociation constants are tabulated and their accuracy ex-
amined. Based on temperature and pressure dependence of dissociation constants,
the thermodynamic functions linked with dissociation process are discussed in a
detail. It also includes description of many aspects connected with compositions
and applications of citrate buffers. Besides, it gives a very extensive number of
references related to citric acid complexes.
Chapter 4 offers an extensive description of the citric acid chemistry. It includes
presentation of total syntheses of citric acid, preparations of labeled citric acid, typi-
cal reactions - neutralization, degradation, oxidation, esterification, formation of
anhydrides, amides, citrate-based siderophores and other compounds.
Chapter 5 contains information about applications and physicochemical proper-
ties of inorganic citrates. These include solubilities in water, boiling temperatures,
freezing points and activity and osmotic coefficients at these temperatures. Pre-
sented vapour pressures of water over unsaturated and saturated solutions of alkali
metal citrates are thermodynamically analyzed to give activities of components in
these systems. From other properties, it also contains sound velocities, densities
of binary and ternary solutions and partition data in two-phase ternary systems,
namely in the alkali metal citrate + aliphatic alcohol + water and alkali metal citrate
+ polyethylene glycol (PEG) + water systems. In addition, it includes the literature
sources leading to data about crystal structure of many inorganic citrates.
Preface ix
There is a number people who helped me in preparing this book and I am grateful
to all of them. First of them is Professor Emanuel Manzurola from Ben-Gurion Uni-
versity of the Negev, Beer Sheva, who during many years participated in our com-
mon research on citric acid and various systems with citrate ions. He also helped to
prepare chemical formulas of this book An exceptional role played Professor Marija
Bĕster-Rogač from Department of Physical Chemistry, Ljubljana University, Slo-
venia who was able using services of the Ljubljana University libraries, to provide
me with a countless number of papers dealing with citric acid or citrates, sometimes
from very obscure journals. She also converted graphically presented experimental
data from the literature to a digital form. I am deeply indebted to Professor Hiro-
kazu Okamoto from Faculty of Pharmacy, Meijo University, Nagoya, Japan who
kindly provided me with his computer program to calculate buffer compositions
and corresponding distribution of species in buffer solutions. Dr. Janez Cezar from
Department of Physical Chemistry, Ljubljana University, Slovenia slightly modi-
fied this program and performed calculations needed to prepare figures represent-
ing behaviour of buffers with citrate ions in Chap. 3. I am grateful for this and for
his continuous help in understanding the buffer action in general. I am very much
obliged to Professor Concetta De Stefano from Department of Inorganic, Analytical
and Physical Chemistry, Messina University, Italy who was extremely cooperative
in obtaining a large number of papers of Italian scientists which were devoted to
the formation of citrate complexes. She also introduced me to the nomenclature ap-
plied when stability constants of complexes are reported. I am thankful to Dr. Olga
Voskresenskaya, Senior Scientist from Joint Institute for Nuclear Research, Dubno,
Russia who helped to obtain a number of not easy available Russian papers. I am
very pleased to mention Professor Maria J. Milewska from Department of Organic
Chemistry, Technical University of Gdańsk, Poland who was very essential in all
aspects related to the synthesis of citric acid and other organic reactions associated
with it. I appreciate very much her help with replacing traditional names of organic
chemical compounds with those coming from the systematic nomenclature system.
I appreciate very much Prof. Gerd Maurer from Department of Mechanical and Pro-
cess Engineering, University of Kaiserslautern, Kaiserslautern, Germany for help-
ing in clarifications of some points associated with aqueous two-phase systems. I
am indebted to Monika Żarska MSc., from Institute of Chemistry, University of
Silesia, Katowice, Poland, who on my request, performed measurements of surface
tension of aqueous solutions of citric acid in order to include them in this book.
Finally, without continuing help, understanding and support coming from my
wife Ira and son Yoram, the appearance of this book would be impossible. I am
deeply thankful to them for their love, patience, support and understanding.
Chemical Engineering Department, Alexander Apelblat
Ben-Gurion University of the Negev,
Beer Sheva, Israel
May, 2012–May, 2014
Contents
1 Introduction .............................................................................................. 1
References .................................................................................................. 6
2 Properties of Citric Acid and Its Solutions ............................................ 13
2.1 Physicochemical Properties of Citric Acid in the Solid State .......... 13
2.2 Melting and Freezing Temperatures of Aqueous Solutions
of Citric Acid .................................................................................... 21
2.3 Boiling Points of Aqueous Solutions of Citric Acid ........................ 27
2.4 Solubility of Citric Acid in Water .................................................... 32
2.5 V apour Pressures of Water Over Saturated Solutions
of Citric Acid .................................................................................... 37
2.6 Solubilities of Gases in Aqueous Solutions of Citric Acid .............. 41
2.7 V olumetric Properties of Aqueous Solutions of Citric Acid ............ 42
2.8 Compressibility Properties of Aqueous Solutions of Citric Acid ..... 53
2.9 T hermodynamic Properties of Aqueous Solutions of Citric Acid .... 67
2.10 Viscosities of Aqueous Solutions of Citric Acid .............................. 83
2.11 Diffusion Coefficients of Citric Acid in Aqueous Solutions ............ 87
2.12 T hermal Conductivities of Aqueous Solutions of Citric Acid .......... 92
2.13 Electrical Conductance of Citric Acid in Aqueous Solutions .......... 94
2.14 Index of Refraction of Aqueous Solutions of Citric Acid ................ 104
2.15 Surface Tension of Aqueous Solutions of Citric Acid ...................... 107
2.16 Solubility of Citric Acid in Organic Solvents .................................. 111
2.17 T wo-Phase Citric Acid–Aliphatic Alcohol–Water Systems ............. 116
2.18 T wo-Phase Citric Acid–Tertiary Amine–Water Systems ................. 126
References ................................................................................................. 130
3 Dissociation Equilibria in Solutions with Citrate Ions ......................... 143
3.1 Mathematical Representation of Citric Acid Dissociation ............... 143
3.2 Distribution of Citrate Ions in Aqueous Solutions of Acidic
and Neutral Citrates .......................................................................... 146
3.3 Dissociation Constants of Citric Acid in Pure Water ....................... 148
3.4 Dissociation Constants of Citric Acid in Electrolyte Solutions ....... 161
xi
xii Contents
3.5 Dissociation Constants of Citric Acid in Pure Organic
Solvents and Organic Solvent-Water Mixtures ................................ 175
3.6 Effect of Pressure on Dissociation Constants .................................. 179
3.7 Citrate Buffers .................................................................................. 180
3.8 Citric Acid Complexes ..................................................................... 192
References ................................................................................................. 195
4 Citric Acid Chemistry .............................................................................. 213
4.1 Chemical Syntheses of Citric Acid .................................................. 213
4.2 Synthesis of Labeled Citric Acid ...................................................... 217
4.3 T hermal Decomposition of Citric Acid ............................................ 219
4.4 Decomposition of Citric Acid by Irradiation ................................... 223
4.5 Oxidation of Citric Acid ................................................................... 225
4.6 Qualitative and Quantitative Determination of Citric Acid ............. 232
4.7 Formation of Citric Acid Anhydrides ............................................... 234
4.8 Esterification and Neutralization Reactions Associated
with Citric Acid ................................................................................ 236
4.9 Formation of Amides Citrate-Based Siderophores and
Other Compounds ............................................................................ 237
References ................................................................................................. 241
5 Physicochemical Properties of Inorganic Citrates ................................ 267
5.1 A pplication of Inorganic Citrates and Their Crystal Structures ....... 267
5.2 Solubilities of Inorganic Citrates in Water ....................................... 272
5.3 A ctivities of Alkali Metal Citrates at Freezing Point
Temperatures .................................................................................... 282
5.4 V apour Pressures of Water Over Saturated Solutions of
Alkali Metal Citrates ........................................................................ 287
5.5 Boiling Points, Activities and Vapour Pressure Lowerings
in Aqueous Solutions of Alkali Metal Citrates ................................. 289
5.6 V olumetric Properties of Aqueous Solutions of Alkali
Metal Citrates ................................................................................... 307
5.7 V olumetric Properties of Ternary Aqueous Solutions with
Alkali Metal Citrates ........................................................................ 319
5.8 Compressibility Properties of Aqueous Solutions of Alkali
Metal Citrates ................................................................................... 325
5.9 V iscosities of Aqueous Solutions of Alkali Metal Citrates .............. 330
5.10 Diffusion Coefficients and Indices of Refraction of Alkali
Metal Citrates in Aqueous Solutions ................................................ 334
5.11 T wo-Phase Alkali Metal Citrate - Aliphatic
Alcohol - Water Systems .................................................................. 336
5.12 T wo-Phase Alkali Metal Citrate - Polyethylene Glycol
(PEG) - Water Systems ..................................................................... 341
References ................................................................................................. 345