Animated Solution for Chemistry - Organic Chemistry: The number of $s{p}^2$-hybridised carbons present in "aspartame" is ............

Imagine you are looking at the molecular blueprint of a popular artificial sweetener, aspartame. At first glance, it might look like a complex web of atoms, but as chemists, we can break it down into familiar functional groups. Our mission is to hunt down every single $s{p}^2$ hybridized carbon atom in this molecule.

To do this, we need a reliable tool. How do we spot an $s{p}^2$ hybridized carbon? The golden rule is to look for carbon atoms that are bonded to exactly three other atoms. In organic structures, this almost always means the carbon is forming one double bond and two single bonds. These carbons adopt a flat, trigonal planar geometry.

Let's scan the molecule from left to right, like reading a book.

Starting on the far left, we encounter a carboxylic acid group ($-COOH$). Look closely at the carbonyl carbon here. It is double-bonded to an oxygen atom and single-bonded to two other groups. This perfectly fits our criteria, making it our first $s{p}^2$ hybridized carbon.

Moving along the main carbon chain, we hit the amide linkage ($-CONH-$). This is the bond that connects the two amino acid building blocks of aspartame. The carbonyl carbon in this amide group is also double-bonded to an oxygen atom. That's our second $s{p}^2$ hybridized carbon.

Continuing further to the right, we find an ester group ($-COOC{H}_3$). Just like the previous two functional groups, this carbonyl carbon features a double bond to oxygen. We have now found our third $s{p}^2$ hybridized carbon.

Finally, let's direct our attention to the bottom of the structure, where a six-membered phenyl ring resides. A benzene ring is a special case. It consists of six carbon atoms, and each one participates in a delocalized $\pi$ system. In any of its resonance structures, each carbon is part of exactly one double bond. Therefore, all six of these carbons are $s{p}^2$ hybridized.

Now, let's tally up our findings to get the final answer: - Carboxylic acid group: $1$ - Amide group: $1$ - Ester group: $1$ - Phenyl ring: $6$

Adding them all together, $1+1+1+6=9$. There are exactly $9$ $s{p}^2$ hybridized carbons in a molecule of aspartame.