Carbonyl Compounds is an important chapter from the NEET perspective when it comes to organic chemistry. On average, about 2 questions are asked every year from this topic making almost 3% of the chemistry part. It is important to go through these study notes before examinations to have a quick revision of the topic. Read More NEET Chemistry Syllabus
Organic Chemistry can be boring for many aspirants, but it also plays a major role in securing a medical seat. Therefore, it is important to study the topic thoroughly and have a quick look at the provided notes for the last time revision of NEET 2021.
Here we will discuss the basic concepts of Carbonyl Compounds, their definitions, basic formula & structure, and their methods of preparations.
Some basic definitions of different Carbonyl Compounds are tabulated below:
What are the Carbonyl Compounds? | The organic compounds containing carbon-oxygen double bond (>C=O) called carbonyl group, are known as Carbonyl Compounds. |
What are Aldehydes? | The Carbonyl Compounds in which the Carbonyl group is attached to a carbon and hydrogen are called Aldehydes. |
What are Ketones? | The Carbonyl Compounds in which the Carbonyl group is attached to two carbon atoms are called Ketones. |
What are Carboxylic Acids? | The carbonyl compounds in which carbon of carbonyl group is bonded to carbon or hydrogen and oxygen of hydroxyl moiety (-OH) are known as Carboxylic Acids. |
What are Acyl Halides? | The carbonyl compounds in which carbon is attached to carbon or hydrogen and halogens are called Acyl Halides. |
What are Amides? | The carbonyl compounds in which carbon is attached to carbon or hydrogen and nitrogen of -NH2 moiety are called Amides. |
The general formulas and structures of Carbonyl Compounds are given below:
Carbonyl Group Structure
Resonating structure of neutral (A) and dipolar (B) Carbonyl group.
Question: In a polar carbonyl group, the carbonyl carbon and carbonyl oxygen act as ………
Correct Answer: D. All of the above.
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Two systems of nomenclature of Aldehydes and Ketones are generally used:
Common nomenclature | IUPAC nomenclature |
---|---|
The common names of most of the aldehydes are derived from their respective carboxylic acids by replacing the “-ic” with “-aldehyde”. | Open chain aliphatic aldehydes and ketones are named by replacing the ending of the respective alkanes by –e with –al and –one respectively. |
The position of the substituents is indicated by the Greek alphabets α, β, γ, δ, etc. | In the case of Aldehydes, the group containing the longest carbon chain is taken into consideration while numbering, starting from the carbon of the Aldehyde group. |
The common names of Aldehydes are derived by naming alkyl or aryl groups that are bonded to the Carbonyl group. | In the case of Ketones, the numbering starts from the end near the carbonyl groups. |
The positions of the substituents are indicated by Greek letters, α α′, β β′ and so on. | IUPAC names are widely accepted names and are universal. |
Common and IUPAC names along with structure and formula are often asked as objective questions in exams. So, it is important to by heart all the common and IUPAC names of some of the common aldehydes and ketones.
Common and IUPAC names of common Aldehydes
Structure | Common name | IUPAC name |
---|---|---|
HCHO | Formaldehyde | Methanal |
CH3CHO | Acetaldehyde | Ethanal |
CH32CHCHO | Isobutyraldehyde | 2-Methylpropanol |
γ-Methylcyclohexanecarbaldehyde | 3-Methylcyclohexanecarbaldehyde | |
CH3CHOCH3CHO | α-Methoxypropionaldehyde | 2-Methoxypropanal |
CH3CH2CH2CH2CHO | Valeraldehyde | Pentanal |
CH2=CHCHO | Acrolein | Prop-2-enal |
Phthalaldehyde | Benzene-1,2-dicarbaldehyde | |
m-Bromobenzaldehyde | 3-Bromobenzenecarbaldehyde or 3-Bromobenzaldehyde |
Common and IUPAC names of Common Ketones
Structure | Common name | IUPAC name |
---|---|---|
CH3COCH2CH2CH2CH3 | Methyl n-propyl ketone | Pentan-2-one |
CH32CHCOCHCH32 | Diisopropyl ketone | 2,4-Dimethylpentan-3-one |
α-Methylcyclohexanone | 2-Methylcyclohexanone | |
CH32C=CHCOCH3 | Mesityl oxide | 4-Methylpent-3-en-2-one |
Question: The common and IUPAC name of CH3CH2CH2CH2CHOis…………….
Correct Answer: A. Valeraldehyde and Pentanal
The Aldehydes and Ketones are generally prepared by four different methods of preparations, which are described briefly below.
The following are the general methods of preparations of Aldehydes and Ketones from the alcohols:
Commonly used oxidizing agents:
The Alcohols are passed through metal catalysts at 573 K temperature. The following reaction takes place during the procedure:
Some of the previous year sample questions for NEET are provided below:
Question: Which of the following reactions will not yield Aldehyde?
Correct Answer: B.
It gives ketone
Nitriles can also be reduced to imines with the help of DIBAL-H, followed by hydrolysis to form respective aldehydes.
Similarly, esters can also be reduced with the help of DIBAL-H to form aldehydes.
Question: Name the given reaction for the method of aldehyde preparation:
Correct Answer: C. Rosenmund reaction
Generally, the following three methods of preparations are used to produce ketones.
Nitriles, on reaction with Grignard reagent followed by hydrolysis, give Ketones.
Question: What is the end product in the given chemical reaction?
Correct Answer: C. Acetone
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Correct Answer: B. Cross Aldol condensation
Correct Answer: A.
Correct answer: C. Benzyl Chloride
Correct answer: D. NaCl
Correct answer: C. Tertiary alcohol
Correct answer: A. Aldehydes and C. Ketones
Correct answer: A. Acetone
Correct answer: B. Sp2
Correct answer: D. Benzaldehyde
Correct answer: C. Benzaldehyde
*The article might have information for the previous academic years, please refer the official website of the exam.