Week 2- Structure, Basic Reaction and Physical of Properties of Organic Compounds PDF

Reaction and Physical of Properties of Organic Compounds Here is where your presentation begins  Table of contents Introduction 1. Difference between organic and inorganic group 2. Definition of functional groups 3. Types of functional groups 1. Hydrocarbons 2. Oxygen-containi...

Reaction and Physical of Properties of Organic Compounds Here is where your presentation begins  Table of contents Introduction 1. Difference between organic and inorganic group 2. Definition of functional groups 3. Types of functional groups 1. Hydrocarbons 2. Oxygen-containing functional groups 3. Nitrogen- containing functional groups 4. Other important functional groups  What is Organic Organic chemistry is concerned with the study Chemistry of the structure and properties of compounds containing carbon.  What is the difference between Organic and Inorganic Compunds  Physical Property of Organic Compounds Relationship between Vapor pressure and boiling point LOW VAPOUR HIGH PRESSURES BOILING POINTS  Physical Property of Organic Compounds Physical properties HIGHER BOILING POINTS depend on the intermolecular of compounds Strength of STRONGER forces INTERMOLEC ULAR FORCES LOWER HIGER VAPOUR MELTING PRESSURE. POINTS  RELATIONSHIP BETWEEN BOILING POINT / MELTING POINT/ VISCOSITY / VAPOUR PRESSURE AND CHAIN LENGTH RELATIONSHIP BETWEEN BOILING POINT/VAPOUR PRESSURE AND BRANCHING Relationship between boiling point/ melting point/ viscosity and TYPE OF FUNCTIONAL GROUP Bonding in Organic Molecules  What are Isomers Isomers — compounds having identical molecular formulas, but different arrangements of atoms. Structural Isomers — the atoms in each molecule are connected in a different order. Tell me what have you notice here What are Functional Groups characteristic arrangement of atoms which define many of the physical and chemical properties of a class of organic compounds. Hydrocarbons Saturated vs Unsaturated  Alkanes Alkanes are saturated hydrocarbons — each carbon holds the maximum number of hydrogen atoms) – Alkanes contain only carbon-carbon single bonds. – General formula: CnH2n+2 (no rings).  Alkanes Properties of Alkanes Alkane molecules are essentially nonpolar. Dispersion forces increase as the number of carbons increases. Boiling point increases as the number of carbon chains increases in the molecule. Have low density; most are less dense than water. Immiscible (not soluble) with water. Generally, have low chemical reactivity The most important chemical reaction of alkanes is a combustion reaction, because branched vs unbranched alkanes n-hexane 2-methyl-pentane 2 Alkenes, Alkynes & Aromatic Compounds Alkenes are hydrocarbons that contain at least 1 carbon-carbon double bond. ○ Examples: 3 Alkenes, Alkynes & Aromatic Compounds Alkynes are hydrocarbons that contain at least 1 carbon-carbon triple bond. ○ Examples: 4 Alkenes, Alkynes & Aromatic Compounds Aromatics are unsaturated ring molecules ○ They are often drawn to look like alkenes, but they behave much differently than alkenes. ○ They have an alternating pattern of double and single bonds within a ring. ○ Benzene is an example 5 Alkenes, Alkynes & Aromatic Compounds The physical properties of all hydrocarbons are the same ○ The have essentially one noncovalent interaction, which is the London dispersion force. ○ They have no electronegative atoms and therefore have No ion/ion interactions No dipole/dipole interactions No hydrogen bonding interactions 6 Alkenes, Alkynes & Aromatic Compounds Naming of Alkenes and Alkynes work the same as for alkanes, with these added rules: ○ The parent chain must include both carbons in all double and triple bonds. Pick the longest chain that also contains all double and triple bonds ○ The -ene ending is used of alkenes ○ The -yne ending is used for alkynes. ○ The number of the first carbon in the double or triple bond is included in the name to locate the double or triple bond. Number the parent chain from the end that is closes to the first Cycloalkanes Molecular Structure: Cycloalkanes consist of closed-ring structures made up of carbon atoms, with each carbon atom bonded to two other carbon atoms in the ring. Cycloalkanes are hydrocarbons, meaning they contain only carbon and hydrogen atoms in their structure. 8 Cycloalkanes When there are three or more carbons in a straight chain, the ends can be joined to make rings. ○ In naming these molecules, the prefix cyclo- is used to indicate the ring: ○ Skeletal structural formulas are used to represent the rings in structural formulas: Cycloalkanes Hydrophobic: Cycloalkanes are typically hydrophobic, meaning they do not mix well with water due to their nonpolar nature. Physical States: Depending on their molecular size and the number of carbon atoms in the ring, cycloalkanes can be found in various physical states at room temperature. For example ○ smaller cycloalkanes are often gases or liquids ○ larger ones can be solids. Cycloalkanes Chemical Reactivity: Cycloalkanes are less reactive than some other functional groups in organic chemistry, such as alkenes or alkynes. However, they can still undergo reactions, including substitution and addition reactions. Boiling Points: Cycloalkanes generally have higher boiling points compared to their linear counterparts (acyclic alkanes) with the same number of carbon atoms.  Cycloalkane s The carbon-carbon single bonds for the carbons in a ring are no longer free to rotate. ○ This leads to a new type of isomer ○ Since the two structures share the same name, they are not constitutional isomers. 31 2 Cycloalkanes Isomers which share the same atomic connections, and therefore, the same IUPAC name are called stereoisomers. ○ When this occurs due to restricted rotation about a covalent bond, they are called geometric isomers ○ The prefix cis- and trans- are used to distinguish geometric isomers. Uses of Cyclohexane, for example, is a common solvent in organic chemistry laboratories.  Oxygen-Containing Functional Groups Groups with oxygen may have a carbonyl (carbon- oxygen double bond) or not. The functional groups without carbonyls are ethers, alcohols, and epoxides. Conversely, these groups with carbonyls are aldehydes, ketones, carboxylic acids, and carboxylic acid derivatives.  Alcohols, Phenols, and Ethers An alcohol has an –OH bonded to an alkyl group; a phenol has an –OH bonded directly to an aromatic ring; an ether has an O bonded to two organic groups. Some Common Alcohols Simple alcohols are very common organic chemicals. They are useful as solvents, antifreeze agents, and disinfectants, and they are involved in the metabolic processes of all living organisms. Methyl alcohol is commonly known as wood alcohol because it was once prepared by heating wood in the absence of air. Today it is made in large quantities by reaction of carbon monoxide with hydrogen. ► Methanol is used to make formaldehyde and methyl tert-butyl ether (MTBE), an octane booster added to gasoline. Methyl alcohol is colorless, miscible with water, and toxic to humans when ingested.  Ethyl alcohol produced by fermentation is called grain alcohol; with methyl alcohol, camphor, or kerosene added it is called denatured alcohol. Industrially, most ethanol is made by hydration of ethylene. Absolute alcohol is 100% ethyl alcohol. Gasohol is a blend of ethyl alcohol and gasoline. Isopropyl alcohol, or rubbing alcohol, is used for rubdowns, as a solvent, as a sterilant for instruments, and as a skin cleanser before drawing blood or giving injections. Less toxic than methyl alcohol, isopropyl alcohol is more toxic than ethyl alcohol.  Ethylene glycol, a diol, is: a toxic, colorless liquid, miscible with water and insoluble in nonpolar solvents. Its two major uses are as antifreeze and as a material for making polyester. The triol, glycerol or glycerin, is: a nontoxic, colorless liquid that is miscible with water. It is used as a sweetener, a moisturizer, in plastics manufacture, in antifreeze and shock-absorber fluids, and as a solvent. Physical Properties of alcohol Solubility: Small alcohols (e.g., methanol, ethanol) are soluble in water due to their ability to form hydrogen bonds. Solubility decreases with increasing carbon chain length. Boiling and Melting Points: Alcohols generally have higher boiling and melting points compared to hydrocarbons of similar molecular weight due to hydrogen bonding. The boiling point increases with increasing carbon chain length. Flammability: Alcohols are flammable, and their flammability increases with decreasing molecular weight and increasing carbon chain branching. Primary alcohols have higher boiling points than secondary and tertiary alcohols. Chemical Properties of alcohol Hydrogen Bonding: Alcohols can form hydrogen bonds with other molecules due to the polar nature of the O-H bond, making them capable of interacting strongly with water and other polar solvents. Reactivity: Alcohols can undergo various chemical reactions, including oxidation, esterification, dehydration, and substitution reactions, depending on their structure and the reagents used Oxidation: Primary and secondary alcohols can be oxidized to form aldehydes or ketones, respectively, using oxidizing agents like potassium permanganate (KMnO4) or chromium(VI) compounds. Esterification: Alcohols can react with carboxylic acids to form esters, which are often used in flavor and fragrance industries. Solubility of Alcohol Solubility decreases with increasing length of the alkyl group. Solubility in water due to hydrogen bonding between alcohol and water molecules.  Acidity of Alcohols React with active metals to form alkoxides. Acidity decreases with electron-donating groups attached to the hydroxyl group.  Dialcohols, or diols, are often called glycols. Ethylene glycol is the simplest glycol; propylene glycol is often used as a solvent for medicines that need to be inhaled or rubbed onto the skin. Classification of Alcohol Alcohols with one substituent are said to be primary, those with two substituents are secondary, and those with three substituents are tertiary. Reactions of Alcohols Alcohols undergo loss of water (dehydration) on treatment with a strong acid catalyst. The –OH group is lost from a C, and an –H is lost from an adjacent C to yield an alkene product: Reactions of Alcohols Primary and secondary alcohols are converted into carbonyl-containing compounds on treatment with an oxidizing agent. A carbonyl group is a functional group that has a C=O. The symbol [O] will indicate a generalized oxidizing agent. An organic oxidation is one that increases the number of C-O bonds and/or decreases the number of C-H bonds. Reactions of Alcohols Primary alcohols are converted either into aldehydes if carefully controlled conditions are used, or into carboxylic acids if an excess of oxidant is used. Reactions of Alcohols Secondary alcohols are converted into ketones on treatment with oxidizing agents. Tertiary alcohols do not normally react with oxidizing agents because they do not have a hydrogen on the carbon atom to which the –OH group is bonded. Phenols Phenol is the name both of a specific compound, hydroxybenzene, and of a family of compounds. Phenols are usually named with the ending - phenol rather than -benzene even though their structures include a benzene ring.  Alcohols undergo oxidation in the presence of an oxidizing agent to produce aldehydes and ketones which upon further oxidation give carboxylic acids.  Phenol is a medical antiseptic first used by Joseph Lister in 1867. Lister showed that the occurrence of postoperative infection dramatically decreased when phenol was used to cleanse the operating room and the patient’s skin.  The medical use of phenol is now restricted because it can cause burns and is toxic. Only solutions with Br > I), the stronger is the acid 35.5 Reactions of Carboxylic Acids (SB p.43) The further away of the substituents from the carboxyl group, the weaker is the acid 35.5 Reactions of Carboxylic Acids (SB p.44) Check Point (a) Match the Ka values: 2.19  10–3 M and 1.26  10–3 M, to the carboxylic acids: CH2FCOOH and CH2BrCOOH. Explain your answer briefly. Answer (a) The greater the Ka value, the stronger is the acid. CH2FCOOH is a stronger acid than CH2BrCOOH. This –F substituent exerts a stronger inductive effect than the –Br substituent, as fluorine is more electronegative than bromine. The –F substituent stabilizes the conjugate base (i.e. CH2FCOOH–) to a greater extent than the –Br substituent. Therefore, CH2FCOOH has a Ka value of 2.19  10–3 M, and CH2BrCOOH has a Ka value of 1.26  10–3 M.  35.5 Reactions of Carboxylic Acids (SB p.44) Check Point (b) Arrange the following acids in ascending order of acidity: CHCl2COOH, CCl3COOH, CH2ClCOOH, CH3COOH Explain the order briefly. Answer (b) CH3COOH < CH2ClCOOH < CHCl2COOH < CCl3COOH The –Cl substituent is an electron-withdrawing group. An increasing number of the –Cl substituent brings about a greater negative inductive effect. Thus, the conjugate base will be stabilized more, and the acidity of the acid increases.  FormationofofSalts Formation Salts Reaction with Active Metals Carboxylic acids react with reactive metals such as Na or Mg to give the corresponding metal carboxylates and hydrogen gas  Reaction with Bases Carboxylic acids react with strong alkalis such as NaOH to form sodium carboxylates and water Examples:  35.5 Reactions of Carboxylic Acids (SB p.45) Carboxylic acids also react weak alkalis such as Na2CO3 or NaHCO3 to form sodium carboxylates, carbon dioxide and water This reaction serves as a test to distinguish carboxylic acids and other acidic organic compounds 35.5 Reactions of Carboxylic Acids (SB p.45) Examples: This reaction serves as a test to distinguish carboxylic acids and other acidic organic compounds  Nomenclature of Nomenclature of Carboxylic Carboxylic Acids Acids and and their their Derivatives Derivatives AcylChlorides Acyl Chlorides Acyl chlorides are named by replacing the final “-ic acid” of the name of the parent carboxylic acid with “-yl chloride” Examples: Formation of Formation of Acyl Acyl Chlorides Chlorides Acyl chlorides are the most reactive amongst the carboxylic acid derivatives They can be prepared by the use of SOCl2, PCl3 or PCl5 in good yields  Formation of Formation of Acyl Acyl Chlorides Chlorides Acyl chlorides can be used to prepare aldehydes, ketones, esters, amides and acid anhydrides in organic synthesis Acyl chlorides are extremely sensitive to moisture, therefore, it must be stored in anhydrous conditions ∵ hydrolyze rapidly to form carboxylic acids  35.6 Reactions of the Derivatives of Carboxylic Acids (SB p.51) Reaction with Water Acyl chlorides are hydrolyzed by water to form the parent carboxylic acids and hydrogen chloride Examples:  35.6 Reactions of the Derivatives of Carboxylic Acids (SB p.51) Reaction with Alcohols Acyl chlorides react with alcohols to give esters and HCl Examples:  Reaction with Ammonia and Amines Acyl chlorides react with ammonia to form amides rapidly Example:  Nomenclature of Carboxylic Acids and their Derivatives Nomenclature of Nomenclature of Carboxylic Carboxylic Acids Acids and and their their Derivatives Derivatives AcidAnhydrides Acid Anhydrides Acid anhydrides are named by dropping the word “acid” from the name of the parent carboxylic acid and then adding the word “anhydride” Examples: 35.6 Reactions of the Derivatives of Carboxylic Acids (SB p.53) ReactionsofofAcid Reactions AcidAnhydrides Anhydrides Reaction with Water Acid anhydrides undergo hydrolysis to form carboxylic acids Example : 35.6 Reactions of the Derivatives of Carboxylic Acids (SB p.53) Reaction with Alcohols Acid anhydrides react with alcohols to form esters in the presence of acid catalyst Example:  Nomenclature of Carboxylic Acids and their Derivatives Nomenclature of Nomenclature of Carboxylic Carboxylic Acids Acids and and their their Derivatives Derivatives Amides Amides Amides that have no substituents on the nitrogen atom are named by replacing “-oic acid” from the parent carboxylic acid with “amide” Substituents on the nitrogen atom of amides are named and the named substituent is preceded by N-, or N,N- Examples: Amines Amines are essentially molecules of ammonia One or more of the hydrogen atoms have been replaced with an alkyl group Structure of Amines Nitrogen atom of amines is trivalent and carries an unshared pair of electrons. Nitrogen orbitals in amines are therefore, sp3 hybridised and the geometry of amines is pyramidal. Each of the three sp3 hybridised orbitals of nitrogen overlap with orbitals of hydrogen or carbon depending upon the composition of the amines. Sources and related content Classification of amine Description of Amides: Amides are organic compounds containing the amide functional group (-CONH2) formed by the condensation of a carboxylic acid and an amine. They are found in a variety of natural and synthetic compounds, including proteins, peptides, and pharmaceuticals. Amides play a crucial role in the structure and function of biomolecules like proteins, as they form the peptide bonds that link amino acids together.  Properties of Amides Physical Properties of Chemical Properties of Amides: Amides: Solubility: Soluble in Amides can form hydrogen polar solvents like water bonds with water and other and organic solvents. molecules due to the Odor: Some amides have presence of a polar C=O bond and a N-H bond. distinctive odors, e.g., Amides are weak bases and acetamide has a faint do not readily donate odor. protons. Amides are relatively stable compared to other carbonyl compounds like aldehydes  Formation of Formation of Amides Amides Ammonia reacts with carboxylic acids to form ammonium salts. The dry salts are heated to dehydrate to give amide The better way to prepare amides is reacting ammonia or amines with acyl chlorides 35.6 Reactions of the Derivatives of Carboxylic Acids (SB p.55) Reaction with Water Amide undergo acid and alkaline hydrolyses to form carboxylic acids and carboxylates respectively Acid hydrolysis: Alkaline hydrolysis:  35.6 Reactions of the Derivatives of Carboxylic Acids (SB p.55) Dehydration Amides are dehydrated by heating with P4O10 to form nitriles Useful synthetic method for preparing nitriles that are not available by nucleophilic substitution reactions between haloalkanes and cyanide ions Thiols and Disulfides Thiols, or mercaptans, are sulfur analogs of alcohols. Skunk scent is caused by the two thiols shown below center and right. The systematic name of a thiol is formed by adding -thiol to the parent name. Thiols and Disulfides Thiols (R-SH) react with mild oxidizing agents to yield a disulfide (R-S-S-R). Cysteine is an amino acid that contains a thiol (-SH) group and is an essential component of hair keratin, the protein that makes up hair strands. Cysteine residues within the keratin protein are involved in the formation of disulfide bonds (S-S) that contribute to the structural integrity of hair. Halogen-Containing Compounds Alkyl halides, R-X, have an alkyl group, R, bonded to a halogen, X. Their common names consist of the name of the alkyl group followed by the halogen name with an -ide ending. Systematic names consider the halogen atom as a substituent on a parent alkane.  Halogenated organic compounds have a variety of medical and industrial uses: -Anesthetics -Solvents, propellants, degreasing agents -Fire extinguishers -Herbicides, fungicides, insecticides  Despite the enormous benefits of halogenated organic compounds, their use has been restricted, and sometimes banned altogether because:  Halogen-containing organic compounds are important in marine organisms; few are significant in human biochemistry. One exception is thyroxine, an iodine- containing hormone secreted by the thyroid gland. ► A deficiency of iodine in the diet leads to a low thyroxine level, which causes a swelling of the thyroid gland called goiter. To ensure adequate iodine in the diet KI is sometimes added to table salt. 123 124 125 126 127  Activity of the day Groupwork make a collage of the different application of the different functional groups