Benzoic acid is a food preservative. The space-filling model for benzoic acid is shown below. Dr

Benzoic acid is a food preservative. The space-filling model...

Key Concepts

Aromaticity

Aromaticity is a property of cyclic, planar molecules with delocalized pi-electron systems that leads to enhanced stability. This concept is crucial when dealing with compounds like benzene, where the electron delocalization is best represented using multiple resonance structures.

Formal Charge Calculation

Formal charge is a bookkeeping tool used to estimate the electron density distribution in a molecule. It is calculated using the formula: Formal charge = (valence electrons) – (non-bonding electrons + 1/2 bonding electrons). Correct assignment of formal charges in resonance structures helps in identifying the most stable electron distributions.

Resonance Structures

Resonance structures are alternative ways of drawing a molecule's electron distribution that cannot be represented by a single Lewis structure. They depict the delocalization of electrons within a molecule, which contributes to its overall stability, and are particularly important in molecules with conjugated systems or aromatic rings.

Lewis Structures

A Lewis structure is a diagram that shows the bonding between atoms of a molecule and the lone pairs of electrons that may exist. It is a fundamental tool in chemistry used to represent the arrangement of atoms, bonds, and electrons, ensuring that each atom satisfies the octet rule when applicable.

Transcript

00:01 So in this problem number 102, the benzoic acid is a food preservative.

00:08 So benzoyic acid is the food preservative.

00:13 So the space filling model of the benzoyic acid is shown below as in the question.

00:19 Problem number 102.

00:21 So draw the loose structure of benzoyic acid including all the resonance structure, which all the atoms have formal charge is zero.

00:29 So first we can see that the benzoic acid is basically c6h5 c .o .h.

00:37 So this is basically acid group.

00:39 So that's why this is known as benzoic acids.

00:43 Or we can write in this way c6 h5 c02h.

00:49 So that means when we draw the structure of this benzoic acids, so its structure is like this is carbon and this is carbon.

01:00 And here carbon here we can see that carbon and then here carbon carbon so basically it's a six -membered ring and then this is carbon and then here double bond oxygen and then this is o and h so this is the structure of benzoyic acid now we can use double bond so it's alternate position single double and single and double so now we can make a hydrogen atom so here one two three four five but here already carbon has make a four bond so no need to write hydrogen in this case and not even in this case so when we see that the total number of electron in benzoyic acid is basically, carbon has four valence electron and total 6 plus 1, 7.

02:13 So 7 into 4.

02:15 So that make 28 electrons.

02:18 And hydrogen, we can see that 5 plus 1, 6.

02:21 So 6 into 1, that is 6.

02:23 And in case of oxygen, 2 oxygen atom, and each oxygen atom has 6 valence electrons, so 6 into 2, which make 12.

02:32 So on adding we get 6 and 4.

02:38 2, 3 and 4.

02:40 So that means total 46 electrons are involved in this structure of benzoyic acid.

02:46 So now we can, we know that oxygen has 6 valence electrons.

02:53 So here, it makes a 2 bonds.

02:56 So that mean we can use 1, 2, 3, 4 electron here.

03:02 And similarly, here 1, 2, 3, 4 electrons here.

03:06 All right so now we can see that we can shift the electrons of this double bond very easily like shifting of electron can take place so here double bond shift electron this here this and here this so basically we shift the electrons of this ring so the resonance resonating structure so this is a symbol of resonance.

03:38 It is basically we draw as carbon, carbon, then carbon, carbon, and then carbon, carbon, carbon, carbon, and then this is carbon, double bond, oxygen, and this is o and h.

04:00 So now we can see that we can shift the electron in this way, bond.

04:06 So that mean here, it's a double.

04:09 Bond and similarly here we can use double bond and similarly here so that mean double bond again as in the alternate position single bond double double single double now we can use hydrogen to satisfy the bond of carbon so here one hydrogen and here one two three carbon mix three bond and one more hydrogen so here one more hydrogen so here one two three four one more hydrogen and one two three four one more so, and the electrons are, these electrons are as it is...

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