Introduction Questions in English

(B) Aldehydes are organic compounds containing a functional group with the structure $-CHO$.
The general molecular formula for saturated aliphatic aldehydes is $C_n H_{2n} O$,where $n$ is the number of carbon atoms $(n \ge 1)$.
For example,if $n=1$,the formula is $CH_2O$ (Formaldehyde,$HCHO$).
If $n=2$,the formula is $C_2H_4O$ (Acetaldehyde,$CH_3CHO$).

(B) ketone is an organic compound containing a carbonyl group $(C=O)$ bonded to two carbon atoms.
$1$. Ethyl ethanoate is an ester $(CH_3COOCH_2CH_3)$.
$2$. Acetophenone is a ketone with the structure $C_6H_5COCH_3$,where the carbonyl group is attached to a phenyl group and a methyl group.
$3$. $N$-Methylphthalimide is an imide.
$4$. Methyl salicylate is an ester.
Therefore,the correct answer is Acetophenone.

(C) simple or symmetrical ketone is one in which the two alkyl or aryl groups attached to the carbonyl carbon $(C=O)$ are identical.
Benzophenone $(C_6H_5-CO-C_6H_5)$ has two phenyl groups attached to the carbonyl carbon,making it a simple (symmetrical) ketone.
Acetophenone $(C_6H_5-CO-CH_3)$,Butanone $(CH_3-CH_2-CO-CH_3)$,and Pentan-$2$-one $(CH_3-CO-CH_2-CH_2-CH_3)$ are mixed (unsymmetrical) ketones because the groups attached to the carbonyl carbon are different.

(B) In the carbonyl group,the $C$ atom is $sp^2$ hybridised and forms three sigma bonds.
The $C-C-O$ bond angle is approximately $120^{\circ}$.
The $C=O$ bond is stronger than the $C=C$ bond in alkenes because oxygen has higher electronegativity than carbon,which results in partial ionic character in the $C=O$ bond,making it stronger.

(C) The compound $CH_2=CH-CHO$ is an unsaturated aldehyde.
Its $IUPAC$ name is $Prop-2-enal$.
Its common name is $Acrolein$.

(A) Acrolein is the simplest unsaturated aldehyde. Its chemical structure consists of a vinyl group attached to an aldehyde group. The chemical formula is $CH_2=CH-CHO$. Therefore,the correct option is $A$.

(A) The chemical formula of Acrolein is $CH_2=CH-CHO$.
It contains both a carbon-carbon double bond (alkene) and an aldehyde group $(-CHO)$.
According to the $IUPAC$ priority order for functional groups,the aldehyde group has higher priority than the alkene group.
Therefore,the main functional group in Acrolein is the aldehyde group.

(C) The structural formula of Diacetone alcohol is shown in the image.
To determine the $IUPAC$ name:
$1$. Identify the longest carbon chain containing the principal functional group (ketone). The chain has $5$ carbons,so the parent alkane is pentane.
$2$. Number the chain from the end closer to the ketone group. The ketone is at position $2$.
$3$. There is a methyl group at position $4$ and a hydroxyl group at position $4$.
$4$. Combining these,the name is $4-$hydroxy$-4-$methylpentan$-2-$one.

(B) The structures of the given compounds are as follows:
$I$. Cinnamaldehyde ($3$-phenylprop-$2$-enal): $C_6H_5-CH=CH-CHO$
$II$. Salicylaldehyde ($2$-hydroxybenzaldehyde): $A$ benzene ring with a $-CHO$ group at position $1$ and a $-OH$ group at position $2$.
$III$. Vanillin ($4$-hydroxy-$3$-methoxybenzaldehyde): $A$ benzene ring with a $-CHO$ group at position $1$,a $-OH$ group at position $4$,and a $-OCH_3$ group at position $3$.
Comparing these with the given options,option $B$ correctly represents the structures of cinnamaldehyde,salicylaldehyde,and vanillin in that order.

(A) In the carbonyl group $(C=O)$,the oxygen atom is more electronegative than the carbon atom. This causes the $\pi$-electrons to shift towards the oxygen atom,resulting in a partial positive charge on the carbon atom and a partial negative charge on the oxygen atom.
The carbon atom,being electron-deficient (partial positive charge),acts as an electrophile.
The oxygen atom,having lone pairs and a partial negative charge,acts as a nucleophile.
Therefore,statements $A$ and $D$ are correct.

(B) Vanillin $(4\text{-hydroxy-}3\text{-methoxybenzaldehyde})$ is an organic compound with the molecular formula $C_8H_8O_3$.
Structurally,it contains an aldehyde group $(-CHO)$,a phenolic hydroxyl group $(-OH)$,and a methoxy group $(-OCH_3)$ attached to a benzene ring.
Thus,the correct set of functional groups is $-CHO, -OH, -OCH_3$.

(C) Mesityl oxide has the chemical structure $(CH_3)_2C=CHCOCH_3$.
To determine the $IUPAC$ name,we identify the longest carbon chain containing the ketone functional group.
The chain has $5$ carbon atoms,so the parent alkane is pentane.
The ketone group is at position $2$,so it is a pentan-$2$-one.
$A$ double bond is present at position $3$,making it a pent-$3$-en-$2$-one.
There is a methyl group at position $4$.
Combining these,the $IUPAC$ name is $4$-methylpent-$3$-en-$2$-one.