The document discusses benzene and its derivatives, including:
- Kekulé's model of benzene and its aromatic properties
- Hückel's rules for determining aromaticity based on π-electrons
- Electrophilic substitution reactions of benzene like halogenation, nitration, sulfonation
- Friedel-Crafts reactions for alkylation and acylation of benzene
- Nomenclature for substituted benzenes including monosubstituted and polysubstituted derivatives
Phenols/OC -II PCI Syllabus/preparation of Phenols/ Sources of Phenols/Qualit...yasar qazi
Phenols/OC -II PCI Syllabus/preparation of Phenols/ Sources of Phenols/Qualitative tests of Phenols
Hi dear students, in this video I had explained about Phenols. I had tried to explain all the points by animations. So don't hasitate to study now, See this video and you will come to know the facts about acidity and basicity of organic compounds. After watching this video it will be very easy to answer the following questions,
What are phenols?
what about acidity of phenols?
Sources of phenols?
Naming of phenols?
qualitative tests of phenols?
Please do subscribe Online ustaad and share this video to as many as possible.
Online Ustaad
https://www.youtube.com/channel/UCzCN5UTEjFAtCBtrcNOWbyA
Reactions of Phenols: https://youtu.be/XJSoCTewg3U
Acidity of Phenols : https://youtu.be/hOh8x_YCsHM
you can also see
Is torrent downloading safe : https://youtu.be/vHjtNnXGztA
How To Make Youtube Thumbnail Free 2020 :https://youtu.be/Mvsl6P8z-Mk
Thumbnail Tips 2020 Hindi :https://youtu.be/H83VNRj_6gg
independence day status 2020 :https://youtu.be/0w7uq4bigFY
how to make you tube cover photo : https://youtu.be/k32Z-lXE7hc
How to cut a music file in 2 minutes :https://youtu.be/2wjfCOfOGGk
Keep watching your own channel online ustaad and give me your suggestions in comment box.
if you find this video helpful then like it, share it and subscribe online ustaad for more helpful & informational videos.
FOLLOW ME AT
dailyreviewz4@gmail.com
FACEBOOK : @onlineustaad4
INSTAGRAM : @online.ustaad
TWITTER : @onlineustaad4
#pcisyllabus #organicchemistry #pharmacy #pci #onlineustaad #tutorial #neetpreparation #bpharmacy #ugguide #bpharmacy3rdsem #pharmacytutorials
Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied by hydrogen or alkyl or aryl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde.
Phenols/OC -II PCI Syllabus/preparation of Phenols/ Sources of Phenols/Qualit...yasar qazi
Phenols/OC -II PCI Syllabus/preparation of Phenols/ Sources of Phenols/Qualitative tests of Phenols
Hi dear students, in this video I had explained about Phenols. I had tried to explain all the points by animations. So don't hasitate to study now, See this video and you will come to know the facts about acidity and basicity of organic compounds. After watching this video it will be very easy to answer the following questions,
What are phenols?
what about acidity of phenols?
Sources of phenols?
Naming of phenols?
qualitative tests of phenols?
Please do subscribe Online ustaad and share this video to as many as possible.
Online Ustaad
https://www.youtube.com/channel/UCzCN5UTEjFAtCBtrcNOWbyA
Reactions of Phenols: https://youtu.be/XJSoCTewg3U
Acidity of Phenols : https://youtu.be/hOh8x_YCsHM
you can also see
Is torrent downloading safe : https://youtu.be/vHjtNnXGztA
How To Make Youtube Thumbnail Free 2020 :https://youtu.be/Mvsl6P8z-Mk
Thumbnail Tips 2020 Hindi :https://youtu.be/H83VNRj_6gg
independence day status 2020 :https://youtu.be/0w7uq4bigFY
how to make you tube cover photo : https://youtu.be/k32Z-lXE7hc
How to cut a music file in 2 minutes :https://youtu.be/2wjfCOfOGGk
Keep watching your own channel online ustaad and give me your suggestions in comment box.
if you find this video helpful then like it, share it and subscribe online ustaad for more helpful & informational videos.
FOLLOW ME AT
dailyreviewz4@gmail.com
FACEBOOK : @onlineustaad4
INSTAGRAM : @online.ustaad
TWITTER : @onlineustaad4
#pcisyllabus #organicchemistry #pharmacy #pci #onlineustaad #tutorial #neetpreparation #bpharmacy #ugguide #bpharmacy3rdsem #pharmacytutorials
Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied by hydrogen or alkyl or aryl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde.
This is Power Point Presentation on Topic "Electrophilic Aromatic Substitution Reactions" as per syllabus of "University of Mumbai" for S.Y. B. Pharmacy (Sem.: IV) students.
General Chemistry of AROMATIC COMPOUNDS
CONTENTS:
-Aromatic compounds and aromaticity.
- Characteristic properties of aromatic compound.
- Nomenclature of derivatives of benzene.
- Benzene.
- Kekule’s structure of Benzene.
X-ray study of the structure of Benzene.
Molecular orbital description of benzene.
- Hückel 4n+2 Rule.
- Resonance of Benzene.
- Preparations of Benzene.
- Reactions of aromatic compound.
- Orientation in electrophilic substitution reactions.
This is Power Point Presentation on Topic "Electrophilic Aromatic Substitution Reactions" as per syllabus of "University of Mumbai" for S.Y. B. Pharmacy (Sem.: IV) students.
General Chemistry of AROMATIC COMPOUNDS
CONTENTS:
-Aromatic compounds and aromaticity.
- Characteristic properties of aromatic compound.
- Nomenclature of derivatives of benzene.
- Benzene.
- Kekule’s structure of Benzene.
X-ray study of the structure of Benzene.
Molecular orbital description of benzene.
- Hückel 4n+2 Rule.
- Resonance of Benzene.
- Preparations of Benzene.
- Reactions of aromatic compound.
- Orientation in electrophilic substitution reactions.
Introduction to benzene, orbital picture, resonance in benzene, Huckel‟s rule
Reactions of benzene - nitration, sulphonation, halogenation- reactivity, Friedel- Craft‟s alkylation- reactivity, limitations, Friedel-Craft‟s acylation.
Substituents, effect of substituents on reactivity and orientation of mono substituted benzene compounds towards electrophilic substitution reaction.
1. Introduction
2. History of benzene
3. Nomenclature
4. Orbital structure
5. Kekule structure
6. Resonance structure
7. Resonance energy and stability 8. Structural evidence
9. Synthetic evidence
10. Analytical evidence
11. Aromaticity and huckle rule
12. Method of preparation of benzene
13. Electrophilic substitution of benzene
14. Classification of substituent 15. Directive effect : Ortho and para director, meta director
16. Reaction of monosubstituted benzene
17. Effect of Substituents on reactivity and orientation of monosubstituted benzene towards electrophilic substitution 18. Structure and uses of BHC,DDT, Saccharine and chloramine
To study the properties, nomenclature and the physical as well chemical reactions of aliphatic and alkyl benzene. Might as well as the usage of benzene in our daily life routine
Benzene has 6π electrons delocalized in 6p orbitals that overlap above and below the plane of the ring. Because benzene’s six pie electrons satisfy Huckel’s rule, benzene is especially stable. Reaction that keep the aromatic ring intact are therefore favoured
I hope You all like it. I hope It is very beneficial for you all. I really thought that you all get enough knowledge from this presentation. This presentation is about materials and their classifications. After you read this presentation you knowledge is not as before.
This presentation has been reported for its great application in Organic synthesis and effects of various substituents. It will be useful in understanding of many organic reaction mechanisms.
Sulphonamides, MOA, SAR, History of development, Nomenclature of the Sulfonamides, Classification, Spectrum of Action of the Sulfonamides,Structure Activity Relationship, Reducing Toxicity, Cotrimoxazole
nalidixic acid, the quinolones, the naphthyridines & the cinnolines, Classification, ISOSTERIC REPLACEMENT
DNA gyrase (Topo II) SAR- substitution variation, Ciprofloxacin
Penicillin Classification, Mechanism of Action, Structure Activity Relationship, Structure of Penicillins, penicillin-binding proteins (PBPs) functional propertiesCross-linking of the peptidoglycan by transpeptidases, Cross-linking of the peptidoglycan by transpeptidases, Shape of penicillin G Penicillin SAR AcylSide Chain Modifications Instability of β-lactams to nucleophiles
Penicillinase-Resistant Penicillins Protein Binding of Penicillins
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
Have you ever wanted a Ruby client API to communicate with your web service? Smithy is a protocol-agnostic language for defining services and SDKs. Smithy Ruby is an implementation of Smithy that generates a Ruby SDK using a Smithy model. In this talk, we will explore Smithy and Smithy Ruby to learn how to generate custom feature-rich SDKs that can communicate with any web service, such as a Rails JSON API.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
1. Organic Chemistry II
Benzene and Its Derivates
DR. S. S. HARAK
ASST. PROF. PHARM. CHEM.
GOKHALE EDUCATION SOCIETY’S
SIR DR. M. S. GOSAVI COLLEGE OF PHARMACEUTICAL EDUCATION & RESEARCH,
NASHIK-5
2. Outline
Aromaticity
Huckel’s rule
The Reactions (Electrophilic
Substitution)
Halogenation
Friedel-Craft’s Reaction
Alkylation and acylation
Nitration and sulphonation
Oxidation and reduction
of benzene derivates
Disubstitution (Ortho, meta,
para directing groups)
Phenol and aniline
The relative acidity of phenol
The relative basicity of aniline
Diazoniums compounds
3.
4. Kekulé’s Model of Benzene
The first structure for benzene, proposed by August Kekulé in
1872
consisted of a six membered ring with alternating single and
double bonds and with one hydrogen bondedto each carbon.
Kekulé further proposed that the ring contains three double bonds
that shift back and forth so rapidly that the two forms cannot be
separated.
Each structure has become known as a Kekulé structure.
5. Kekulé’s Model of Benzene
His proposal also accounted for the fact that the bromination of bromobenzene gives
three (and only three) isomeric dibromobenzenes.
If benzene contains three double bonds,, his critics asked,
why doesn’t it show the reactions typical of alkenes?
Why doesn’t it add three moles of bromine to form 1,2,3,4,5,6-hexabromocyclohexane?
Why, instead, does benzene react by substitution rather than addition?
6. The Main Features
The bond length is between C – C and C=C (1.38A)
Due to delocalised electron (resonance structure)
7. The Main Features
The structure is planar
Each carbon has p orbital that forms π bonding
Maximum bonding benzene should planar
9. Aromaticity (Hückel’s Rules)
Huckel’s rules define the classification of aromatic and non-aromatic
molecule.
The criteria of aromatic molecule:
All the atoms are sp2 hybridised and in planar cyclicarrangement.
All atoms are sp2 but not acyclic.
Hence, non-aromatic
There is non-sp2 atom.
Hence, non-aromatic
All atoms are sp2 and acyclic.
Hence, could be aromatic
10. Huckel’s rules
Huckel’s rule
Number of π-electrons is (4n+2),
How to calculate π-electrons?
based on the structure, p-orbitals in sp2 arrangement has 1electron
Has 6 π-electrons (4n+2, n=1)
Hence, aromatic
Has 4 π-electrons (4n, n=1)
Hence, anti-aromatic
11. Huckel’s Rule (summary)
Does the molecule have
non-sp2 atoms?
NO YES
How many π-
electrons in the
molecule?
4n+2 Not 4n+2
aromatic Anti-
aromatic
non-aromatic
13. Huckel’s rule
Which molecules are aromatic?
6 π-electrons
Is this molecule aromatic?
2 π-electrons
14. The reactions
Benzene undergoes electrophilic substitution
Doesn’t undergo electrophilicaddition
The consequence of aromatic properties
15. The reactions - Halogenation
Halogenation. E.g. chlorination
Via:
The presence of Lewis acid (e.g. AlCl3) helps benzene to react with Cl2
16. The Reactions – Friedel-Crafts
Reaction
Friedel-Crafts Reaction (Alkylation)
To substitute with hydrocarbon chain
Via:
Electrophilic
generation
17. Friedel-Crafts Reaction
There is a problem for this reaction when longer alkyl halide isused
Rearrangement of the electrophile (carbocation)
Trying to find the most stable carbocation
18. Friedel-Crafts Reaction (Acylation)
To substitute with R-CO –
Via:
Electrophilic generation acylium ion
stabilised by resonance. Both structures are valid.
23. Oxidation
The Oxidation of toluene
R
OH
O
1) KMnO4, OH-
, Heat
2) H3O+
Where R is alkyl group
The Reduction ofAniline
NO2 NH2
Fe
HCl
aniline
24. Diazonium formation
Diazonium salts is a good precursor compound for:
Halogenation
formation of phenol
deamination
coupling reaction of arenediazonium salts
Formation of Diazonium salts
NH2 N
+ N
Cl
-
NaNO2, HCl
0 - 15 o
C, H2O
26. Halogenation
The bromination of benzene: All electrophilic aromatic substitution reactions share a common
mechanism.
This mechanism consists of a series of steps.
1. An electrophile — an electron‐seeking reagent — is generated.
2. For the bromination of benzene reaction, the electrophile is the Br+ ion generated by the
reaction of the bromine molecule with ferric bromide, a Lewis acid.
27. BROMINATION OF BENZENE
This mechanism consists of a series of steps.
1. An electrophile — an electron‐seeking reagent — is generated.
2. The electrophile attacks the π electron system of the benzene ring to form a
nonaromatic carbocation.
28. BROMINATION OF BENZENE
3. The positive charge on the carbocation that is formed is delocalized throughout the
molecule.
4. The aromaticity is restored by the loss of a proton from the atom to which the bromine
atom (the electrophile) has bonded.
5. Finally, the proton reacts with the FeBr 4
− to regenerate the FeBr 3 catalyst and form the
product HBr.
30. The nitration of benzene
In another example of an electrophilic aromatic substitution reaction, benzene
reacts with a mixture of concentrated nitric and sulfuric acids to create
nitrobenzene.
31. The mechanism for the nitrobenzene reaction occurs in six steps.
1. Sulfuric acid ionizes to produce a proton.
2. Nitric acid accepts the proton in an acid‐base reaction.
3. The protonated nitric acid dissociates to form a nitronium ion ( +NO 2).
32. 4. The nitronium ion acts as an electrophile and is attracted to the π electron
system of the benzene ring.
5. The nonaromatic carbocation that forms has its charge delocalized around the
ring.
33. 6. The aromaticity of the ring is reestablished by the loss of a proton from the
carbon to which the nitro group is attached.
34. The reaction of benzene with concentrated sulfuric acid at room temperature
produces benzenesulfonic acid.
The mechanism for the reaction that produces benzenesulfonic acid occurs in the
following steps:
1. The sulfuric acid reacts with itself to form sulfur trioxide, the electrophile.
This reaction takes place via a three‐step process:
The sulfonation of benzene
36. FORMATION OF BENZENE SULPHONIC
ACID
C.
2. The sulfur trioxide is attracted to the π electron system of the benzene
molecule.
3. Formation of benzene sulphonic acid
37. Monosubstituted Benzenes
Monosubstituted alkylbenzenes are named as derivatives of benzene; an
example is ethylbenzene.
The IUPAC system retains certain common names for several of the simpler
monosubstituted alkylbenzenes. Examples are toluene (rather than
methylbenzene) and styrene (rather than phenylethylene):
38. The common names phenol, aniline, benzaldehyde, benzoic acid, and anisole are also
retained by the IUPAC system:
The physical properties of substituted benzenes vary depending on the nature of the
substituent.
Alkylbenzenes, like other hydrocarbons, are nonpolar and thus have lower boiling points
than benzenes with polar substituents such as phenol, aniline, and benzoic acid.
The melting points of substituted benzenes depend on whether or not their molecules can
be packed close together.
Benzene, which has no substituents and is flat, can pack its molecules very closely, giving it
a considerably higher melting point than many substituted benzenes.
39. the substituent group derived by the loss of an H from benzene is a phenyl group (Ph);
that derived by the loss of an H from the methyl group of toluene is a benzyl group (Bn):
40. In molecules containing other functional groups, phenyl groups and benzyl
groups are often named as substituents:
41. Test your Knowledge
Write a structural formula for the product formed by Friedel–Crafts alkylation or
acylation of benzene with
42. Strategy
Utilize the fact that the halogenated reagent in Friedel–Crafts reactions will normally
form a bond with benzene at the carbon bonded to the halogen (Br or Cl).
Therefore, to predict the product of a Friedel–Crafts reaction, replace the halogen in
the haloalkane or acyl halide with the benzene ring.
One thing to be wary of, however, is the possibility of rearrangement once the
carbocation is formed.
46. Substituted Benzenes
When two substituents occur on a benzene ring, three constitutional isomers are
possible.
We locate substituents either by numbering the atoms of the ring or by using the
locators
ortho, meta, and para.
The numbers 1,2- are equivalent to ortho (Greek: straight);
1,3- to meta (Greek: after); and
1,4- to para (Greek: beyond).
47. Substituted Benzene Nomenclature
When one of the two substituents on the ring imparts a special name to the
compound, as, for example, toluene, phenol, and aniline, then we name the
compound as a derivative of that parent molecule.
In this case, the special substituent occupies ring position number 1.
The IUPAC system retains the common name xylene for the three isomeric
dimethylbenzenes.
When neither group imparts a special name, we locate the two substituents and
list them in alphabetical order before the ending -benzene.
The carbon of the benzene ring with the substituent of lower alphabetical ranking
is numbered C-1.
49. Polysubstituted Benzenes
When three or more substituents are present on a ring, we specify their locations by numbers.
If one of the substituents imparts a special name, then the molecule is named as a derivative
of that parent molecule.
If none of the substituents imparts a special name, we number them to give the smallest set of
numbers and list them in alphabetical order before the ending -benzene.
In the following examples, the first compound is a derivative of toluene, and the second is a
derivative of phenol.
Because there is no special name for the third compound, we list its three substituents in
alphabetical order, followed by the word benzene:
51. Strategy
First, determine whether one of the substituents imparts a special name to the benzene
compound (e.g., toluene, phenol, aniline).
Identify all substituents and list them in alphabetical order.
Use numbers to indicate relative position.
The locators ortho, meta, or para can be used for disubstituted benzenes.
52. Solution
Write names for these compounds:
(a) 3-Iodotoluene or m-iodotoluene
(b) 3,5-Dibromobenzoic acid
(c) 1-Chloro-2,4-dinitrobenzene
(d) 3-Phenylpropene
53. TYPES OF SUBSTITUTION IN AROMATIC RINGS
Substituted rings are divided into two groups based on the type of the substituent
that the ring carries:
Activated rings: the substituents on the ring are groups that donate electrons.
Deactivated rings: the substituents on the ring are groups that withdraw
electrons.
54. ACTIVATING GROUPS
Examples of activating groups in the relative order from the most activating group to the
least activating:
-NH2, -NR2 > -OH, -OR> -NHCOR> -CH3 and other alkyl groups
with R as alkyl groups (CnH2n+1)
Examples of deactivating groups in the relative order from the most deactivating to the
least deactivating:
-NO2, -CF3> -COR, -CN, -CO2R, -SO3H > Halogens
with R as alkyl groups (CnH2n+1)
The order of reactivity among Halogens from the more reactive (least deactivating
substituent) to the least reactive (most deactivating substituent) halogen is:
F> Cl > Br > I
55. HALOGENATION ORDER OF REACTIVITY
The order of reactivity of the benzene rings toward the electrophilic substitution
when it is substituted with a halogen groups, follows the order of
electronegativity.
The ring that is substituted with the most electronegative halogen is the most
reactive ring ( less deactivating substituent ) and the ring that is substituted with
the least electronegativity halogen is the least reactive ring ( more deactivating
substituent), when we compare rings with halogen substituents.
Also the size of the halogen effects the reactivity of the benzene ring that the
halogen is attached to. As the size of the halogen increase, the reactivity of the
ring decreases.
56. Direction of the reaction
The activating group directs the reaction to the ortho or para position,
The electrophile substitute the hydrogen that is on carbon 2 or carbon 4.
The deactivating group directs the reaction to the meta position,
i.e. the electrophile substitute the hydrogen that is on carbon 3 with the exception
of the halogens that is a deactivating group but directs the ortho or para
substitution.
57. Substituents determine the reaction direction
RESONANCE
Resonance effect is the conjugation between the ring and the substituent, which means
the delocalizing of the π electrons between the ring and the substituent.
INDUCTIVE EFFECT
Inductive effect is the withdraw of the sigma ( the single bond ) electrons away from the
ring toward the substituent, due to the higher electronegativity of the substituent
compared to the carbon of the ring
58. Activating groups (ortho/para directors)
When the substituents like -OH have an unshared pair of electrons, the resonance effect is stronger than the inductive effect
which make these substituents stronger activators, since this resonance effect direct the electron toward the ring.
In cases where the substituents is esters or amides, they are less activating because they form r
By looking at the mechanism above, we can see how groups donating electron direct the ortho, para electrophilic substitution.
Since the electrons locating transfer between the ortho and para carbons, then the electrophile prefer attacking the carbon
that has the free electron.
Inductive effect of alkyl groups activates the direction of the ortho or para substitution, which is when s electrons gets pushed
toward the ring.
Resonance structure that pull the electron density away from the ring.
59. Substitution Summary
The reaction of a substituted ring with an activating group is faster than benzene.
On the other hand, a substituted ring with a deactivated group is slower than benzene.
Activating groups speed up the reaction because of the resonance effect.
The presence of the unpaired electrons that can be donated to the ring, stabilize the carbocation in
the transition state.
Thus; stabilizing the intermediate step, speeds up the reaction; and this is due to the decrease of the
activating energy.
On the other hand, the deactivating groups, withdraw the electrons away from the carbocation
formed in the intermediate step, thus;
the activation energy is increased which slows down the reaction.
60. Deactivating group (meta directors)
The deactivating groups deactivate the ring by the inductive effect in the presence of an electronegative
atom that withdraws the electrons away from the ring.
we can see from the mechanism above that when there is an electron withdraw from the ring, that leaves
the carbons at the ortho, para positions with a positive charge which is unfavorable for the electrophile, so
the electrophile attacks the carbon at the meta positions.
Halogens are an exception of the deactivating group that directs the ortho or para substitution.
The halogens deactivate the ring by inductive effect not by the resonance even though they have an
unpaired pair of electrons. The unpaired pair of electrons gets donated to the ring, but the inductive effect
pulls away the s electrons from the ring by the electronegativity of the halogens.
66. Halogenation of Phenols
Due to a highly activating effect of the hydroxyl group in phenols, they undergo halogenation even in
the absence of Lewis acids. When phenols are treated with bromine in the presence of a solvent of low
polarity like CHCl3 at low temperatures, monobromophenols are formed.
When phenol is treated with bromine water, a white precipitate of 2, 4, 6-tribromophenol is formed.
Editor's Notes
Because all of the carbons and hydrogens of Kekulé’s structure are equivalent, substituting bromine for any one of the hydrogens gives the same compound.
Thus, Kekulé’s proposed structure was consistent with the fact that treating benzene with bromine in the presence of ferric chloride gives only one compound with the molecular formula C6 H5 Br.