Aldehydes and ketones are compounds containing a carbonyl group, these compounds are collectively called carbonyl compounds. There is a double bond between carbon and oxygen. Due to the difference in electronegativity of C and O, the bond is polar. In aldehydes, carbonyl groups are bonded to two hydrogens or to one hydrogen and one alkyl or aryl group, whereas in ketones they are bonded to alkyl and aryl groups.

• The general formula for Aldehydes is R—CH=O.
• The general formula for Ketones is R—CR’=O.

The functional group of aldehydes —CH=O is also called the aldehydic group while the functional group of ketones —CR’=O is called the Ketonic group. If the two groups are the same in a ketone (R = R’), the ketone is called a simple ketone. On the other hand, if the two groups are different, the ketone is called a mixed ketone.

Carboxylic Acids are the compounds that contain Carboxyl functional group in their molecules. The name carboxyl is derived from 2 words carbo which means carbonyl and oxyl which means hydroxyl group. The carboxylic acids are aliphatic (R-COOH) or aromatic (Ar-COOH) depending upon whether the —COOH group is attached to the aliphatic alkyl chain or aryl group. The general formula is 

Carboxylic acid

Many higher members of aliphatic carboxylic acids (C₁₂ – C₁₈) are called fatty acids because they are obtained by hydrolysis of fats. Carboxylic acids act as starting materials for many other important organic compounds such as esters, amides, etc.

Table of Contents

Physical Properties of Aldehydes and Ketones

The Physical Properties of aldehydes and ketones are:

Physical State

Methanal is a pungent-smelling gas. Aldehydes and Ketones contain up to eleven carbon atoms are colorless liquids while higher members are solids.

Smell

Lower aldehydes have unpleasant odors, aldehydes and ketones have pleasant smells. When the size of the molecule increases the odor becomes less pungent and more fragrant. Many aldehydes and ketones have been used in blending perfumes and flavoring agents.

Solubility 

Aldehydes and Ketones with up to 4 carbon atoms are miscible in water because of the presence of hydrogen bonding between the polar carbonyl group and water molecules. The solubility of aldehydes and ketones decreases by increasing the length of the alkyl chain. All aldehydes and ketones are fairly soluble in organic solvents and ketones are good solvents themselves.

Boiling Points

The boiling points of aldehydes and ketones are higher than non-polar compounds or weak polar compounds of comparable molecular masses. The boiling points are lower than alcohols or carboxylic acids because aldehydes and ketones are polar compounds having sufficient intermolecular dipole-dipole interactions between opposite ends of C=O dipoles. 

Therefore, Dipole-Dipole interactions are weaker than the intermolecular hydrogen bonding in alcohols and carboxylic acids. Boiling points of aldehydes and ketones are low than the alcohols and carboxylic acids of the molecular masses.

Among these carbonyl compounds, Ketones have higher boiling points than isomeric aldehydes because of the presence of two electrons releasing groups around carbonyl carbon which makes them more polar.

Vander Waals dispersion forces

As the molecule lengthens, the number of electrons increases, and the attraction between the molecules increases. The boiling points of aldehydes and ketones increase as the number of carbon atoms increases.

Vander Waals dipole-dipole attraction

The presence of carbon-oxygen double bonds in both aldehydes and ketones. They are polar in nature. There are also attractive forces between permanent dipoles and molecules. This is why aldehydes and ketones have a higher boiling point than hydrocarbons.

Physical Properties of Carboxylic acids 

The physical properties of carboxylic acids are:

Physical State

The first 3 members of carboxylic acids are colorless liquids and have pungent smells. They are colorless waxy solids. Benzoic Acids are colorless solids.

Solubility

The first four members are very soluble in water and solubility decreases with rising molecular masses. All are soluble in alcohol. Benzoic Acid is soluble in cold water but it is soluble in hot water, ether. 

The Solubility of lower members of carboxylic acids is due to hydrogen bonding. The solubility of carboxylic acids decreases with an increase in the size of the alkyl group or molecular masses because of reduced polarity and hindrance provided by large bulky groups to the carboxylic group for taking part in hydrogen bonding.  e.g. Pentanoic acids and hexanoic acids are soluble in water.  

Aromatic acids are almost insoluble in water. e.g. Benzoic acid is the simplest aromatic carboxylic acid that is insoluble in cold water. Both aliphatic and aromatic carboxylic acids are soluble in less polar organic solvents such as benzene.

Boiling Points

The carboxylic acids have higher boiling points because of the presence of intermolecular hydrogen bonding. The hydrogen bonds are not broken completely in the vapor phase. Mostly carboxylic acids exist as dimers in the vapor phase and in aprotic solvents. They have higher boiling points than the aldehydes, ketones, and alcohols. 

e.g. The boiling point of Ethanoic Acid is 391 K whereas that of propanol is 370 K.

There are two reasons that boiling points of carboxylic acids is higher than the alcohols:

• When we compared to alcohols, the O— H bond in carboxylic acid is more strongly polarised because of the presence of an adjacent electron-withdrawing carbonyl group. That’s why carboxylic acids can form stronger hydrogen bonds.
• The molecules of carboxylic acids are held together by two hydrogen bonds and form cyclic dimers.

In the monocarboxylic acids, the boiling point increase with the increase in molecular masses because as the size of the alkyl group increases the magnitude of attractive forces increases, and hence boiling points increase.

e.g. HCOOH acid has a boiling point of 373 K, CH₃COOH acid has a boiling point of 391 K, C₂H₅COOH acid has a boiling point of 424 K.

Melting Points

The melting points of carboxylic acids increase irregularly with an increase in molecular masses. The first ten members of carboxylic acids have melting points that contain an even number of carbon atoms is higher than the next lower and higher member contains an odd number of carbon atoms. 

e.g. CH₃CH₂COOH acid contains 3 carbons that have a melting point of 251 and CH₃CH₂CH₂COOH acid contains four carbons that have a melting point of 267. The melting and boiling points of aromatic acids are higher than aliphatic acids of comparable molecular masses.

Sample Questions(FAQs)

Question 1: Why do aldehydes and ketones have high dipole moments?

Answer: 

The carbonyl group in aldehydes and ketones contains a double bond between carbon and oxygen atoms as oxygen is more electronegative than carbon. So oxygen gets a negative charge while carbon gets a positive charge therefore, aldehydes and ketones have high dipole moments.

Question 2: Is the preparation of acetaldehyde from ethyl alcohol it is distilled out as soon as it formed. Explain it.

Answer: 

Yes, To prevent its oxidation it is distilled out as soon as possible because aldehyde is easily oxidizable to acetic acid.

Question 3: Why aliphatic aldehyde do not show position isomers?

Answer: 

Aliphatic aldehydes do not show position isomers because in the case of aliphatic aldehydes the —CHO group is always present at the end.

Question 4: Why are boiling points of carboxylic acids is higher than alcohols?

Answer: 

Carboxylic acids have higher boiling points than alcohols because it has greater hydrogen bonding in acids than alcohols and as a result, the molecules of carboxylic acids are held together by two hydrogen bonds.

Question 5: Which is a more reactive carboxylic acid or aldehyde?

Answer: 

The carbonyl carbon in the acyl group is less electrophilic than aldehyde.

Question 6: Why is carboxylic acid is acidic?

Answer: 

Carboxylic acid is acidic because of hydrogen in the —COOH group.

Question 7: Why is aldehyde more acidic than ketone?

Answer: 

Aldehyde is more acidic than Ketone because of the lower electron-donating effect of the proton compared to the alkyl group of the ketone.

Neeraj Anand, Param Anand

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

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CBSE Class 12 Chemistry Syllabus Download PDF

Below is the CBSE Class 12 Syllabus along with the marking scheme and time duration of the Chemistry exam.

CBSE Class 12 Chemistry Practical Syllabus along with Marking Scheme

The following is a breakdown of the marks for practical, project work, class records, and viva. The total number of marks for all parts is 15. The marks for both terms are provided in the table below.

CBSE Class 12 Chemistry Syllabus (Chapter-wise)

Unit -1: Solutions

• Raoult's law.
• Colligative properties - relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure, determination of molecular masses using colligative properties, abnormal molecular mass.
• Solutions, Types of solutions, expression of concentration of solutions of solids in liquids, solubility of gases in liquids, solid solutions.
• Van't Hoff factor.

Unit -2: Electrochemistry

• Redox reactions, EMF of a cell, standard electrode potential
• Nernst equation and its application to chemical cells
• Relation between Gibbs energy change and EMF of a cell
• Kohlrausch's Law
• Electrolysis and law of electrolysis (elementary idea)
• Dry cell-electrolytic cells and Galvanic cells
• Conductance in electrolytic solutions, specific and molar conductivity, variations of conductivity with concentration.
• Lead accumulator
• Fuel cells

Unit -3: Chemical Kinetics

• Rate of a reaction (Average and instantaneous)
• Rate law and specific rate constant
• Integrated rate equations and half-life (only for zerfirst-order order reactions)
• Concept of collision theory (elementary idea, no mathematical treatment)
• Factors affecting rate of reaction: concentration, temperature, catalyst;
• Order and molecularity of a reaction
• Activation energy
• Arrhenius equation

Unit -4: d and f Block Elements  

• Lanthanoids- Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences.
• Actinoids- Electronic configuration, oxidation states and comparison with lanthanoids.
• General introduction, electronic configuration, occurrence and characteristics of transition metals, general trends in properties of the first-row transition metals – metallic character, ionization enthalpy, oxidation states, ionic radii, color, catalytic property, magnetic properties, interstitial compounds, alloy formation, preparation and properties of K2Cr2O7 and KMnO4.

Unit -5: Coordination Compounds  

• Coordination compounds - Introduction, ligands, coordination number, color, magnetic properties and shapes
• The importance of coordination compounds (in qualitative analysis, extraction of metals and biological system).
• IUPAC nomenclature of mononuclear coordination compounds.
• Bonding
• Werner's theory, VBT, and CFT; structure and stereoisomerism

Unit -6: Haloalkanes and Haloarenes  

• Haloarenes: Nature of C–X bond, substitution reactions (Directive influence of halogen in monosubstituted compounds only). Uses and environmental effects of - dichloromethane, trichloro methane, tetrachloromethane, iodoform, freons, DDT.
• Haloalkanes: Nomenclature, nature of C–X bond, physical and chemical properties, optical rotation mechanism of substitution reactions.

Unit -7: Alcohols, Phenols and Ethers   

• Phenols: Nomenclature, methods of preparation, physical and chemical properties, acidic nature of phenol, electrophilic substitution reactions, uses of phenols.
• Ethers: Nomenclature, methods of preparation, physical and chemical properties, uses.
• Alcohols: Nomenclature, methods of preparation, physical and chemical properties (of primary alcohols only), identification of primary, secondary and tertiary alcohols, mechanism of dehydration, and uses with special reference to methanol and ethanol.

Unit -8: Aldehydes, Ketones and Carboxylic Acids   

• Carboxylic Acids: Nomenclature, acidic nature, methods of preparation, physical and chemical properties; uses.
• Aldehydes and Ketones: Nomenclature, nature of carbonyl group, methods of preparation, physical and chemical properties, mechanism of nucleophilic addition, the reactivity of alpha hydrogen in aldehydes, uses.

Unit -9: Amines    

• Diazonium salts: Preparation, chemical reactions and importance in synthetic organic chemistry.
• Amines: Nomenclature, classification, structure, methods of preparation, physical and chemical properties, uses, and identification of primary, secondary and tertiary amines.

Unit -10: Biomolecules     

• Proteins -Elementary idea of - amino acids, peptide bond, polypeptides, proteins, structure of proteins - primary, secondary, tertiary structure and quaternary structures (qualitative idea only), denaturation of proteins; enzymes. Hormones - Elementary idea excluding structure.
• Vitamins - Classification and functions.
• Carbohydrates - Classification (aldoses and ketoses), monosaccharides (glucose and fructose), D-L configuration oligosaccharides (sucrose, lactose, maltose), polysaccharides (starch, cellulose, glycogen); Importance of carbohydrates.
• Nucleic Acids: DNA and RNA.

The syllabus is divided into three parts: Part A, Part B, and Part C. Part A consist of Basic Concepts of Chemistry, which covers topics such as atomic structure, chemical bonding, states of matter, and thermochemistry. Part B consists of Topics in Physical Chemistry, which includes topics such as chemical kinetics, equilibrium, and electrochemistry. Part C consists of Topics in Organic Chemistry, which covers topics such as alkanes, alkenes, alkynes, and aromatic compounds.

Basic Concepts of Chemistry:

• Atomic structure: This section covers the fundamental concepts of atomic structure, including the electronic configuration of atoms, the Bohr model of the atom, and the wave nature of matter.
• Chemical bonding: This section covers the different types of chemical bonds, including ionic, covalent, and metallic bonds, as well as the concept of hybridization.
• States of the matter: This section covers the three states of matter - solid, liquid, and gas - and the factors that influence their properties.
• Thermochemistry: This section covers the principles of thermochemistry, including the laws of thermodynamics and the concept of enthalpy.

Chapters in Physical Chemistry:

• Chemical kinetics: This section covers the study of the rate of chemical reactions and the factors that influence it, including the concentration of reactants, temperature, and the presence of catalysts.
• Equilibrium: This section covers the principles of chemical equilibrium, including the concept of Le Chatelier's principle and the equilibrium constant.
• Electrochemistry: This section covers the principles of electrochemistry, including the concept of half-cell reactions, galvanic cells, and electrolysis.

Chapters in Organic Chemistry:

• Alkanes: This section covers the properties and reactions of alkanes, including their structure, isomerism, and combustion.
• Alkenes: This section covers the properties and reactions of alkenes, including their structure, isomerism, and addition reactions.
• Alkynes: This section covers the properties and reactions of alkynes, including their structure, isomerism, and addition reactions.
• Aromatic compounds: This section covers the properties and reactions of aromatic compounds, including their structure, isomerism, and electrophilic substitution reactions.

In addition to the topics covered in the syllabus, the CBSE Class 12 Chemistry exam also tests students on their analytical and problem-solving skills, as well as their ability to apply the concepts learned in the classroom to real-world situations.

Students can also check out the Tips for the Class 12 Chemistry Exam. They can easily access the Class 12 study material in one place by visiting the CBSE Class 12 page at ANAND CLASSES (A School Of Competitions). Moreover, to get interactive lessons and study videos, download the ANAND CLASSES (A School Of Competitions) App.

Frequently Asked Questions on CBSE Class 12 Chemistry Syllabus

Q1

How many chapters are there in the CBSE Class 12 Chemistry as per the syllabus?

There are 10 chapters in the CBSE Class 12 Chemistry as per Syllabus. Students can learn all these chapters efficiently using the study materials provided at ANAND CLASSES (A School Of Competitions).

Q2

What is the marking scheme for CBSE Class 12 Chemistry practical exam according to the syllabus?

The marking scheme for CBSE Class 12 Chemistry practical exam, according to the syllabus, is 8 marks for volumetric analysis, 8 marks for salt analysis, 6 marks for the content-based experiment, 4 marks for the project and viva and 4 marks for class record and viva.

Q3

Which is the scoring chapter in Chemistry as per CBSE Class 12 syllabus?

The chapter Electrochemistry in Chemistry is the scoring chapter as per CBSE Class 12 syllabus.