Collision theory proposes that chemical reactions occur when molecules collide with sufficient kinetic energy to overcome the activation energy barrier. The rate of reaction is directly proportional to the number and frequency of effective collisions between reactant molecules possessing energy greater than or equal to the activation energy. However, collision theory has limitations as it does not account for factors like molecular orientation, bond cleavage and formation, or the complexities of reactions involving multi-atomic molecules. It also often overestimates actual reaction rates compared to experimental values.
This is useful to post graduate students. It gives detail explanation about Transition State Theory and Lindemann Theory- derivation, application, limitation
A carbene is any neutral carbon species which contains a non-bonding valance pair of electrons.
Contributed by Alison Brown & Nathan Buehler, Undergraduates, University of Utah
This is useful to post graduate students. It gives detail explanation about Transition State Theory and Lindemann Theory- derivation, application, limitation
A carbene is any neutral carbon species which contains a non-bonding valance pair of electrons.
Contributed by Alison Brown & Nathan Buehler, Undergraduates, University of Utah
THE PERICYCLIC REACTION THE MOST COMMON TOPIC INCLUDE THE SYLLABUS OF MANY SCIENCE STUDY INCLUDING BSC, MSC , PHARMA STUDY, AND MORE HENCE WE ARE COVERED ALL THE DATA OF IT HOPE THIS WILL MAKE READER EASY.
The ionic strength of a solution is a measure of the concentration of ions in that solution. Ionic compounds, when dissolved in water, dissociate into ions. The total electrolyte concentration in solution will affect important properties such as the dissociation constant or the solubility of different salts
Quantum yield, experimental arrangement, reasons for high and low Quantum yield, problems, photochemical reactions, kinetics of photochemical decomposition of HI, photosensitized reaction, mechanism of photosensitization,
CONTENTS
INTRODUCTION
CONCEPTS OF WALSH DIAGRAM
APPLICATION IN TRIATOMIC MOLECULES
[IN AH₂ TYPE OF MOLECULES(BeH₂,BH₂,H₂O)]
INTRODUCTION
Arthur Donald Walsh FRS The introducer of walsh diagram (8 August 1916-23 April 1977) was a British chemist, professor of chemistry at the University of Dundee . He was elected FRS in 1964. He was educated at Loughborough Grammar School.
Walsh diagrams were first introduced in a series of ten papers in one issue of the Journal of the Chemical Society . Here, he aimed to rationalize the shapes adopted by polyatomic molecules in the ground state as well as in excited states, by applying theoretical contributions made by Mulliken .
Unit –II : Chemical Dynamics Potential energy surfaces, Kinetic isotopic effe...RamiahValliappan2
Potential energy surfaces, Kinetic isotopic effects - Dynamics of unimolecular reactions – Lindemann-Hinshelwood – Rice Ramsperger Kassel (RRK) theory and Rice Ramsperger Kassel – Marcus (RRKM) theory. Study of fast reactions by laser, relaxation, flash Photolysis and nuclear magnetic resonance methods. LFERs -Hammett equation, Taft equation, separation of polar, resonance and steric effects.
THE PERICYCLIC REACTION THE MOST COMMON TOPIC INCLUDE THE SYLLABUS OF MANY SCIENCE STUDY INCLUDING BSC, MSC , PHARMA STUDY, AND MORE HENCE WE ARE COVERED ALL THE DATA OF IT HOPE THIS WILL MAKE READER EASY.
The ionic strength of a solution is a measure of the concentration of ions in that solution. Ionic compounds, when dissolved in water, dissociate into ions. The total electrolyte concentration in solution will affect important properties such as the dissociation constant or the solubility of different salts
Quantum yield, experimental arrangement, reasons for high and low Quantum yield, problems, photochemical reactions, kinetics of photochemical decomposition of HI, photosensitized reaction, mechanism of photosensitization,
CONTENTS
INTRODUCTION
CONCEPTS OF WALSH DIAGRAM
APPLICATION IN TRIATOMIC MOLECULES
[IN AH₂ TYPE OF MOLECULES(BeH₂,BH₂,H₂O)]
INTRODUCTION
Arthur Donald Walsh FRS The introducer of walsh diagram (8 August 1916-23 April 1977) was a British chemist, professor of chemistry at the University of Dundee . He was elected FRS in 1964. He was educated at Loughborough Grammar School.
Walsh diagrams were first introduced in a series of ten papers in one issue of the Journal of the Chemical Society . Here, he aimed to rationalize the shapes adopted by polyatomic molecules in the ground state as well as in excited states, by applying theoretical contributions made by Mulliken .
Unit –II : Chemical Dynamics Potential energy surfaces, Kinetic isotopic effe...RamiahValliappan2
Potential energy surfaces, Kinetic isotopic effects - Dynamics of unimolecular reactions – Lindemann-Hinshelwood – Rice Ramsperger Kassel (RRK) theory and Rice Ramsperger Kassel – Marcus (RRKM) theory. Study of fast reactions by laser, relaxation, flash Photolysis and nuclear magnetic resonance methods. LFERs -Hammett equation, Taft equation, separation of polar, resonance and steric effects.
This is a lecture is a series on combustion chemical kinetics for engineers. The course topics are selections from thermodynamics and kinetics especially geared to the interests of engineers involved in combusition
This slide completely describes you about the stuff include in it and also everything about chemical engineering. Fluid Mechanics. Thermodynamics. Mass Transfer Chemical Engineering. Energy Engineering, Mass Transfer 2, Heat Transfer,
activation energy of biological systemKAUSHAL SAHU
SOME GENERAL TERM
FREE ENERGY
ENDERGONIC REACTION
EXERGONIC REACTION
ACTIVATION ENERGY
DEFINITION
TRANSITION STATE
WHERE DOES ACTIVATION ENERGY COME FROM?
DETERMINING THE ACTIVATION ENERGY THROUGH ARREHINIUS EQUATION
EFFECTS OF TEMPERATURE ON ACTIVATION ENERGY
NEGATIVE ACTIVATION ENERGY
EFFECTS OF ENZYMES ON ACTIVATION ENERGY
CONCLUSION
REFERENCES
B. Sc. Part - I (Sem-II) Unit-IV (A) Phenols by Dr Pramod R Padolepramod padole
A) PHENOLS: Methods of formations a) from aniline & b) from cumene. Acidic character, Reaction of Phenols- a) Carboxylation (Kolbe’s reaction), b) Fries Rearrangement, c) Claisen Rearrengement and d) Reimer – Tiemann reaction.
B.Sc. Sem-II Unit-III (B) Aryl halides by Dr Pramod R Padolepramod padole
Aryl Halides: Synthesis chlorobenzene from benzene, phenol, and benzene diazonium chloride, Synthesis of benzyl chloride from toluene and benzyl alcohol, Reactions of both with aqueous KOH, NH3, and sodium ethoxide, Comparison of the reactivity of chlorobenzene and benzyl chloride. Benzyne intermediate mechanism.
B.Sc. (Sem-II) Unit-III (A) Alkenyl Halides by Dr Pramod R Padolepramod padole
Alkenyl Halides: Synthesis of vinyl chloride from acetylene and allyl chloride from propylene, Reactions of both with aqueous and alcoholic KOH, Comparison of the reactivity of vinyl and allyl chloride.
B. Sc. Sem - I Unit-IV (D) Orientation by Dr Pramod R Padolepramod padole
Orientation: Effect of substituent groups. Activating and deactivating groups. Theory of reactivity and orientation on the basis of inductive and resonance effects (-CH3, -OH, -NO2 and –Cl groups).
B.Sc. Sem-I Unit-IV Mechanism of electrophilic aromatic substitution by Dr P...pramod padole
Mechanism of Electrophilic Aromatic Substitution: Nitration, Friedal Craft Alkylation and Acylation.Nuclear and Side Chain
Halogination, Birch Reduction
Sem - I Unit-III C) Aliphatic Hydrocarbons By Dr Pramod R Padolepramod padole
C) Aliphatic Hydrocarbons:
a) Alkanes: Methods of formation: i) Wurtz reaction & ii) Corey-House reaction. Chemical reactions: i) Halogenation (With mechanism),
ii) Aromatisation.
b) Alkenes: Methods of formation (With mechanism): i) Dehydrohalogenation of alkyl halides (E1 & E2), ii) Dehydration of alcohols.
Chemical reactions: Electrophilic & free radical addition of HX and X2 (With mechanism).
c) Alkynes: Preparation from vicinal and germinal dihalides. Chemical reactions: Hydrogenation.
d) Alkadienes : Classification, 1,3-Butadiene: Preparation from cycolhexene, Reactions: Addition of H2, Br2 & HBr.
Dyes, Drugs & Pesticides by Dr Pramod R Padolepramod padole
A] Dyes: Classification on the basis of structure and mode of application, Preparation and uses of Methyl orange, Crystal violet, Phenolphthalein , Alizarin and Indigo.
B) DRUGS:
Analgesic and antipyretics: Synthesis and uses of phenylbutazone. Sulpha drugs: Synthesis and uses of sulphanilamide and sulphadiazine. Antimalarials: Synthesis of chloroquine from 4,7-dichloroquinoline and its uses.
C] Pesticides: Insecticides: Synthesis and uses of malathion. Herbicides: Synthesis and uses of 2,4-dichloro phenoxy acetic acid (2,4-D). Fungicides: Synthesis and uses of thiram (tetramethyl thiuram disulphide).
Semester - I C) Aliphatic Hydrocarbons by Dr Pramod R Padolepramod padole
C) Aliphatic Hydrocarbons:
a) Alkanes: Methods of formation: i) Wurtz reaction & ii) Corey-House reaction. Chemical reactions: i) Halogenation (With mechanism),
ii) Aromatisation.
b) Alkenes: Methods of formation (With mechanism): i) Dehydrohalogenation of alkyl halides (E1 & E2), ii) Dehydration of alcohols.
Chemical reactions: Electrophilic & free radical addition of HX and X2 (With mechanism).
Semester - I C) Aliphatic Hydrocarbons by Dr Pramod R Padolepramod padole
C) Aliphatic Hydrocarbons:
a) Alkanes: Methods of formation: i) Wurtz reaction &
ii) Corey-House reaction. Chemical reactions: i) Halogenation (With mechanism), ii) Aromatisation.
b) Alkenes: Methods of formation (With mechanism): i) Dehydrohalogenation of alkyl halides (E1 & E2), ii) Dehydration of alcohols. Chemical reactions: Electrophilic & free radical addition of HX and X2 (With mechanism).
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
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.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Chemical dynamics, intro,collision theory by dr. y. s. thakare
1. 1
Dr. Y. S. THAKARE
M.Sc. (CHE) Ph D, NET, SET
Assistant Professor in Chemistry,
Shri Shivaji Science College, Amravati
Email: yogitathakare_2007@rediffmail.com
CHEMICAL DYNAMICS
COLLISION THEORY
5. THEORIES OF REACTION RATES
1885-1889 1916-1920 1931-1937 1921-1952
ARRHENIUS
THEORY
COLLISION
THEORY
MODIFIED
COLLISION
THEORY
ABSOLUTE REACTION RATE
THEORY/ ACTIVATED
COMPLEX THEORY/
TRANSITION STATE THEORY
UNIMOLECULAR
THEORIES
Wynne-Jones
& Eyring
H. Eyring,
M. G. Evans &
M. Polanyi
6. Model for Kinetics
Arrhenius Theory
Effect of Temperature
Collision Theory
Rate determined by particle collisions;
Collision frequency and energy
Modified Collision Theory
Steric requirements
Transition State Theory
How reactants convert to products
Unimolecular Theory
8. .
In 1884, based on this work, he submitted
a 150-page dissertation on electrolytic
conductivity to Uppsala for the
doctorate. It did not impress the
professors, among whom was Per
Teodor Cleve, and he received a fourth
class degree, but upon his defence it
was reclassified as third class. Later,
extensions of this very work would
earn him the Nobel Prize in Chemistry.
9. Many of these conceptual and experimental difficulties
would disappear with the brilliant work of van’t Hoff,
who introduced the concept of order of reaction and,
through it, the possibility of knowing the mechanism of a
chemical reaction just on the basis of chemical kinetics In
fact, van’t Hoff used the term molecularity for what we
would call today reaction order (the power to which a
concentration of a component enters into the rate
equation). When referring to the actual concept of
molecularity , this author used the explicit expression “the
number of molecules that participate in the reaction” The
Term order is due to Ostwald. Van’t Hoff received the
first Nobel Prize in 1901 for his discovery of the laws
of chemical dynamics
10. Chemical dynamic
Introduction: -
Collision theory is proposed by Arrhenius and Van't Hoff.
According to this theory the rate of reaction directly proportional to number
of collision per minute time.
1) Colliding molecule must possess sufficient K.E. Greater than or equal to
activation molecule energy to cause the reaction.
2) The reacting molecule must collide with proper orientation.
Explanation: -
• The molecule must collide with sufficient kinetic energy (K.E).
14. FACTORS AFFECTING RATE OF CHEMICAL REACTIONS
The rate of a chemical reaction is affected by several factors like:
1) Concentration of reactants
2) Pressure
3) Temperature
4) Catalyst
5) Nature of reactants
6) Orientation of reacting species
7) Surface area
8) Intensity of light
9) Nature of solvent
15. Arrhenius Equation
k: rate constant
Ea: activation energy (minimum required)
T: absolute temperature
R: universal gas constant=8.314JK-1mol-1
A: orientation factor or Arrhenius constant
Frequency factor or pre-exponential factor
Energy & orientation requirements for reaction
RT
Ea
Aek
16.
17. Van-Hoff Rule:
10
1
2
1
2
t
t
t
t
t
k
k
If t2t1
t
t
k
k 10
Temperature coefficient:
The ratio of rate constants of a reaction at two different temperatures
separated by 10°C'
18. CATALYST
Catalyst is a substance which alters the rate of a reaction
without being consumed or without undergoing any chemical
change during the reaction.
A catalyst increases the rate of reaction by providing a new
path with lower activation energy (Ea’) for the reaction.
20. Ea
ACTIVATION ENERGY - Ea
The Activation Energy is the minimum energy required for a reaction to take place
The area under the curve beyond Ea corresponds to the number of molecules with
sufficient energy to overcome the energy barrier and react.
MAXWELL-BOLTZMANN
DISTRIBUTION OF
MOLECULAR ENERGY
NUMBER OF
MOLECULES WITH
SUFFICIENT
ENERGY TO
OVERCOME THE
ENERGY BARRIER
INCREASING TEMPERATURE
MOLECULAR ENERGY
NUMBEROFMOLECUESWITH
APARTICULARENERGY
21. Explanation
increasing the temperature gives more particles an energy greater than Ea
more reactants are able to overcome the energy barrier and form products
a small rise in temperature can lead to a large increase in rate
T1
T2
TEMPERATURE
T2 > T1
Ea
MAXWELL-BOLTZMANN
DISTRIBUTION OF
MOLECULAR ENERGY
INCREASING TEMPERATURE
MOLECULAR ENERGY
NUMBEROFMOLECUESWITH
APARTICULARENERGY
EXTRA
MOLECULES WITH
SUFFICIENT
ENERGY TO
OVERCOME THE
ENERGY BARRIER
22.
23. ASSUMPTIONS : COLLISION THEORY
The molecules are HARD SPHERE
For a Reaction to occur between molecules, the two molecules must collide
Not all collisions produce reaction; instead, reaction occur if and only if the RELATIVE
TRANSLATIONAL KINETIC ENERGY exceeds THRESHOLD ENERGY
The MAXWELL-BOLTZMANN Distribution of Molecular Velocities is maintained
during the reaction
Certain Steric requirements should be fulfilled
The rate to be proportional to the rate of collisions, and therefore to the mean speed of
molecules
The collision theory of gases gives the rate constant for bimolecular gas-phase reactions;
A reaction occurs on the collision of two molecules only if they possess a certain minimum
amount of energy in excess to the normal energy of the molecules.
The collision between the molecules other than activated molecules do not lead to chemical
reaction at all.
The minimum energy in excess to their normal energy which the molecules must possess
before chemical reaction on collision is known as and equal to the activation energy.
For the formation of product reactant molecule must collide with proper orientation.
24.
25.
26.
27.
28.
29. Collision Theory (Bimolecular Collsions)
Z: no. of bimolecular collisions per second
fa: fraction with Ea
P: fraction with correct orientation
Ea: activation energy
pfZrate a
30.
31. Limitations of collision theory
1) It is applicable for the simple gases reaction only.
2) It is also applicable to the reaction in solution having reaction species exist in
simple molecule only.
3) Calculated values for the rate constant are usually too high compared with
measured values
4) The value of rate constant calculated from collision theory is equal to the observed
for the simple gaseous reaction only. For the reaction having complex molecule the
calculated rate is very large than that of observed rate.
5) There is no method of determine the (rho) (probability) for a reaction whose rate
constant has not been determine experimentally.
6) Collision theory is considering only the K.E. of colliding molecule there is no
reason why rotational and vibrational energy of molecule should be ignoring.
7) The collision theory is silent on clevage and formation of bond involved in the
reaction.
8) For the reaction involving complex molecule the experimental rate constant is quite
different from the calculate values.
9) Calculate value of (rho) from the structure and properties of the reacting molecule
is not in complete arrangement.
10) Measured activation energies are lower than the energies of the bonds that have to
be broken in reactions
11) Collision theory does not provide any prediction of p, the “steric factor”