This document discusses metal-ligand bonding, including:
1) Drawing and labeling the molecular orbital diagram for a M-L6 complex, specifically [Co(NH3)6]3+.
2) Discussing metal-carbonyl, metal-hydride, metal-halide, and metal-carbene bonding, including types, synthesis, and reactions of each.
3) Explaining the mechanism of the formation of metalacycles from alkenes and carbenes, which is the key reaction in alkene metathesis.
Organometallic Reactions and CatalysisRajat Ghalta
Organometallic compounds undergo a rich variety of reactions (oxidative addition, reductive elimination, cyclometalization, migratory insertion, carbonylation, hydrometallation hydrate elimination, etc ) that can sometimes be combined into useful homogeneous catalytic cycles. In this presentation, I have discussed organometallic reactions of particular importance for synthetic and catalytic processes like the oxo process (hydroformylation), heck coupling reaction, Wilkinson’s Catalyst
(Hydrogenation) etc.
Organometallic Reactions and CatalysisRajat Ghalta
Organometallic compounds undergo a rich variety of reactions (oxidative addition, reductive elimination, cyclometalization, migratory insertion, carbonylation, hydrometallation hydrate elimination, etc ) that can sometimes be combined into useful homogeneous catalytic cycles. In this presentation, I have discussed organometallic reactions of particular importance for synthetic and catalytic processes like the oxo process (hydroformylation), heck coupling reaction, Wilkinson’s Catalyst
(Hydrogenation) etc.
Introductory PPT on Metal Carbonyls having its' classification,structure and applications.This is a basic level PPT specially prepared for UG/PG Chemistry students.
Dioxygen complexes, dioxygen as ligand Geeta Tewari
This presentation describes about the preparation, properties, bonding modes, classification and applications of metal Dinitrogen Complexes. Also explains the MO diagram of molecular nitrogen.
7. In many respects metal binding is similar to the binding of a prot.pdfezhilvizhiyan
7. In many respects metal binding is similar to the binding of a proton. For instance the N- atom
of thiocyanate can be protonated to produce (H-NCS). Similarly, protonation of the cyanide
anion (CN-) can be observed at the C-atom to produce H-CN. In apparent contrast to this
analogy, metal coordination to (NCS) can be observed at either N- or S- atoms (M-NCS and
NCS-M) whereas protonation only occurs at the N-atom. Provide an explanation for this
behavior. Similarly, why is the cyanide anion only capable of binding metals and protons at the
C-atom?
Solution
SCN- shares its negative charge approximately equally between sulfur and nitrogen (-S-CN or
S=C=N-). As a consequence, thiocyanate can bind either sulfur or nitrogen center. it is an
ambidentate ligand. [SCN] can also bridge two (MSCNM) or even three metals.
Carbon atom of CO has nonbonding (or weakly anti-bonding) sp-hybridized electron pair which
is make bond with metal. And also, the highest occupied molecular orbital (HOMO) of CO
shows electron density more in carbon of CO. Due to this reason metal coordinate with C of CO.
Metal ......CO bonding explained in below.
Carbon monoxide binds to transition metals using \"synergistic * back-bonding.\" The bonding
has three components, giving rise to a partial triple bond (in CO). A coordination bond arises
from overlap of the nonbonding (or weakly anti-bonding) sp-hybridized electron pair on carbon
with a blend of d-, s-, and p-orbitals on the metal. A pair of bonds arises from overlap of filled
d-orbitals on the metal with a pair of -antibonding orbitals projecting from the carbon atom of the
CO, this back binding requires that the metal have d-electrons, and that the metal is in a
relatively low oxidation state (<+2) which makes the back donation process favorable.
• Ligands
– an ion or molecule which donates electron density to a metal
atom/ion to form a complex
- Lewis base bonded (coordinated) to a metal ion in a coordination complex.
• Coordination Complex
– a central metal atom/ion and its set of ligands
– often an ion itself
• Coordination Compounds
– a neutral species made up in some part of a complex
– often the salt of a coordination complex
• Coordination Number
– the number of ligands in the primary or inner shell of ligands
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Introductory PPT on Metal Carbonyls having its' classification,structure and applications.This is a basic level PPT specially prepared for UG/PG Chemistry students.
Dioxygen complexes, dioxygen as ligand Geeta Tewari
This presentation describes about the preparation, properties, bonding modes, classification and applications of metal Dinitrogen Complexes. Also explains the MO diagram of molecular nitrogen.
7. In many respects metal binding is similar to the binding of a prot.pdfezhilvizhiyan
7. In many respects metal binding is similar to the binding of a proton. For instance the N- atom
of thiocyanate can be protonated to produce (H-NCS). Similarly, protonation of the cyanide
anion (CN-) can be observed at the C-atom to produce H-CN. In apparent contrast to this
analogy, metal coordination to (NCS) can be observed at either N- or S- atoms (M-NCS and
NCS-M) whereas protonation only occurs at the N-atom. Provide an explanation for this
behavior. Similarly, why is the cyanide anion only capable of binding metals and protons at the
C-atom?
Solution
SCN- shares its negative charge approximately equally between sulfur and nitrogen (-S-CN or
S=C=N-). As a consequence, thiocyanate can bind either sulfur or nitrogen center. it is an
ambidentate ligand. [SCN] can also bridge two (MSCNM) or even three metals.
Carbon atom of CO has nonbonding (or weakly anti-bonding) sp-hybridized electron pair which
is make bond with metal. And also, the highest occupied molecular orbital (HOMO) of CO
shows electron density more in carbon of CO. Due to this reason metal coordinate with C of CO.
Metal ......CO bonding explained in below.
Carbon monoxide binds to transition metals using \"synergistic * back-bonding.\" The bonding
has three components, giving rise to a partial triple bond (in CO). A coordination bond arises
from overlap of the nonbonding (or weakly anti-bonding) sp-hybridized electron pair on carbon
with a blend of d-, s-, and p-orbitals on the metal. A pair of bonds arises from overlap of filled
d-orbitals on the metal with a pair of -antibonding orbitals projecting from the carbon atom of the
CO, this back binding requires that the metal have d-electrons, and that the metal is in a
relatively low oxidation state (<+2) which makes the back donation process favorable.
• Ligands
– an ion or molecule which donates electron density to a metal
atom/ion to form a complex
- Lewis base bonded (coordinated) to a metal ion in a coordination complex.
• Coordination Complex
– a central metal atom/ion and its set of ligands
– often an ion itself
• Coordination Compounds
– a neutral species made up in some part of a complex
– often the salt of a coordination complex
• Coordination Number
– the number of ligands in the primary or inner shell of ligands
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
In this book, we use conservation of energy techniques on a fluid element to derive the Modified Bernoulli equation of flow with viscous or friction effects. We derive the general equation of flow/ velocity and then from this we derive the Pouiselle flow equation, the transition flow equation and the turbulent flow equation. In the situations where there are no viscous effects , the equation reduces to the Bernoulli equation. From experimental results, we are able to include other terms in the Bernoulli equation. We also look at cases where pressure gradients exist. We use the Modified Bernoulli equation to derive equations of flow rate for pipes of different cross sectional areas connected together. We also extend our techniques of energy conservation to a sphere falling in a viscous medium under the effect of gravity. We demonstrate Stokes equation of terminal velocity and turbulent flow equation. We look at a way of calculating the time taken for a body to fall in a viscous medium. We also look at the general equation of terminal velocity.
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
1. Assignment 1 Metal-Ligand Bonds
1. a) Draw and label the general molecular orbital diagram for a M-L6
complex ion, [Co(NH3)6]3+
. Identify all the orbitals used for bonding,
nonbonding and antibonding.
Solution:
Figure 1:MO diagram for M-L6 ([Co(NH3)6]3+
complex
i. Bonding Orbitals: a1g, eg(dx2
-y2
, dz2
), t1u
ii. Non-bonding Orbitals: T2g (dxy, dyz,dxz)
iii. Anti-bonding orbitals: eg
*
, A1g
*
, T1u
*
2. Discuss the following M-L bonding under subtopics: Types, Synthesis
and reactions.
(i) Metal-Carbonyls.
Solution:
The carbonyl ligand (CO) distinguishes itself from other ligands in many
respects. For example, unlike the alkyl ligands, the carbonyl (CO) ligand
is unsaturated thus allowing not only the ligand to σ−donate but also to
2. accept electrons in its π* orbital from d metal orbitals and thereby
making the CO ligand π−acidic. The other difference lies in the fact that
CO is a soft ligand compared to the other common σ−and π−basic
ligands like H2O or the alkoxides (RO−), which are considered as hard
ligands. Being π−acidic in nature, CO is a strong field ligand that
achieves greater d−orbital splitting through the metal to ligand π−back
donation. A metal−CO bonding interaction thus comprises of a CO to
metal σ−donation and a metal to CO π−back donation (Figure ).
the extent of the metal to CO π−back donation is almost equal to or even
greater than the extent of the CO to metal σ−donation in metal carbonyl
complexes. This observation is in agreement with the fact that low
valent−transition metal centers tend to form metal carbonyl complexes.
Figure 2: Electronic structure of CO and carbonyl complexes. Shading represents occupied orbitals (a) and (b)
building up CO from C and O, each atom having two p orbitals and two sp hybrids. In (a), the dots represent the
electrons occupying each orbital in the C and O atoms. In (b), only one of the two mutually perpendicular sets of
π orbitals is shown. (c) An MO diagram showing a π bond of CO. (d) Valence bond representations of CO and the
MCO fragment. (e) An MO picture of the MCO fragment. Again, only one of the two mutually perpendicular sets
of π orbitals is shown
Preparations of CO Complexes
The common methods of the preparation of the metal carbonyl compounds are;
i. Directly using CO
The main requirement of this method is that the metal center must be in a reduced
low oxidation state in order to facilitate CO binding to the metal center through
metal to ligand π−back donation.
3. ii. Using CO and a reducing agent
This method is commonly called reductive carbonylation and is mainly used for the
compounds having higher oxidation state metal centers. The reducing agent first
reduces the metal center to a lower oxidation state prior to the binding of CO to
form the metal carbonyl compounds
iii. From carbonyl compounds
This method involves abstraction of CO from organic compounds like the alcohols, aldehydes
and CO2.
Reactions of Metal-Carbonyls
typical reactions are shown in Eqs. 4.8–4.13. All of these depend on the polarization of the CO
on binding, and so change in importance as the coligands and net charge change. For example,
types 1 and 3 are promoted by the electrophilicity of the CO carbon and type 2 by
nucleophilicity at CO oxygen.
i. Nucleophilic attack on carbon
These reactions give carbenes or carbenelike intermediates. The reaction of Eq. 4.10 is
particularly important because it is one of the rare ways in which the tightly bound CO can
be removed to generate an open site at the metal. In this way a ligand L , which would
normally not be sufficiently strongly binding to replace the CO, can now do so.’
ii. Electrophilic attack at oxygen
Protonation of this Re carbonyl occurs at the metal, as is most often the case, but
the bulkier acid, AlMe3, prefers to bind at the CO oxygen
iii.
Migratory insertion reaction
4. Bridging CO Groups
CO has a high tendency to bridge two metals (see the example below):
The electron count remains unchanged on going from 4.4 to 4.5. The 15e CpFe(CO)
fragment is completed in 4.4 by an M−M bond, counted as a 1e contributor to each metal,
and a terminal CO counting as 2e. In 4.5, on the other hand, we count 1e from each of the
two bridging CO (µ2-CO) groups and 1e from the M−M bond. The bridging CO is not entirely
ketonelike because an M−M bond seems almost always to accompany a CO bridge. The CO
stretching frequency in the IR spectrum falls to 1720–1850 cm−1 on bridging.
(ii) Metal-Hydrides
Solution:
Metal hydrides occupy an important place in transition metal organometallic chemistry
as the M−H bonds can undergo insertion reactions with a variety of unsaturated organic
substrates yielding numerous organometallic compounds with M−C bonds. Not only the
metal hydrides are needed as synthetic reagents for preparing the transition metal
organometallic compounds but they also are required for important hydride insertion
steps in many catalytic processes.
The metal hydride moieties are easily detectable in H NMR as they appear high field of
TMS in the region between 0 to 60 ppm, where no other resonances appear. The
hydride moieties usually couple with metal centers possessing nuclear spins. Similarly,
the hydride moieties also couple with the adjacent metal bound phosphine ligands, if at
all present in the complex, exhibiting characteristic cis (J = 15 − 30 Hz) and trans (J = 90 −
150 Hz) coupling constants. In the IR spectroscopy, the M−H frequencies appear
between (1500 − 2200) cm but their intensities are mostly weak. Crystallographic
detection of metal hydride moiety is difficult as hydrogen atoms in general are poor
scatterer of X−rays. Located adjacent to a metal atom in a M−H bond, the detection of
hydrogen atom thus becomes challenging and as a consequence the X−ray
crystallographic method systematically underestimates the M−H internuclear distance
by ~ 0.1 Å.
Synthesis
The main synthetic routes to hydrides are shown in Eqs. 3.27– 3.33:
a. Protonation Reaction
For this reaction to occur the metal center has to be basic and electron rich.
5. b. From Hydride donors
Generally for this method, a main group hydride is reacted with metal halide.
c. From H2:
This method involves oxidative addition of H and thus requires metal centers that
are capable of undergoing the oxidative addition step.
d. From a ligand
This method takes into account the β−elimination that occur in a variety of metal
bound ligand moieties, thereby yielding a M−H bond.
Reactions
Metal hydrides are reactive species kinetically and thus participate in a variety of
transformations. Hydride transfer and insertion are closely related; the former
implies that a hydridic hydride is attacking an electrophilic substrate like the ones
discussed below. (Eqs 3.34-3.37)
a. Deprotonation
The deprotonation reaction can be achieved by a hydride moiety resulting in the
formation of H gas as shown below
b. Hydride transfer and insertion:
In this reaction a hydride transfer from a metal center to formaldehyde resulting
in the formation of a metal bound methoxy moiety is observed as shown below
c. H atom transfer
An example of hydrogen atom transfer reaction is given below
Bridging Hydrides
The metal hydrides usually show two modes of binding, namely terminal and
bridging. In case of the bridging hydrides, the hydrogen atom can bridge
between two or even more metal centers and thus, the bridging hydrides often
display bent geometries.
6. σ−complexes
σ−complexes are rare compounds, in which the σ bonding electrons of a X−H
bond further participate in bonding with a metal center (X = H, Si, Sn, B, and P).
The σ complexes thus exhibit an askewed binding to a metal center with the
hydrogen atom, containing no lone pair, being more close to the metal center
and thereby resulting in a side−on structure. Many times if the metal center is
electron rich, then further back donation to the σ* orbital of the metal bound
X−H moiety may occur resulting in a complete cleavage of the X−H bond.
(iii) Metal-Halides
Solution:
(iv) Metal-Carbenes
Solutions
Carbenes are highly reactive hexavalent species that exist in two spin
states, i.e. (i) in a singlet form, in which two electrons are paired up and (ii) in a
triplet form, in which the two electrons remain unpaired. Of the two, the singlet
form is the more reactive one. The instability of carbene accounts for its unique
reactivity like that of the insertion reaction. The singlet carbene and the triplet
carbene bind differently to metals, with the singlet one yielding Fischer type
carbene complexes while the triplet one yielding Schrock type carbene
complexes.
Synthesis
Carbene complexes can be prepared by the following methods.
i. by the reaction with electrophiles
ii. by H−
/H+
abstraction reactions as shown below
iii. from low−valent metal complexes
3. The formation of metalacycles from alkenes and carbenes is the key
reaction in alkene metathesis. Explain the mechanism of this reaction.