Aldehydes and Ketones: Naming + Properties

Summary

This script delves into the chemistry of aldehydes and ketones, highlighting their structural similarities and differences, particularly the position of the double-bonded oxygen. It explains the nomenclature of these compounds, emphasizing the importance of the carbon chain length and the placement of functional groups. The script also touches on the polarity and reactivity of these molecules, noting their lower boiling points compared to alcohols due to the absence of hydrogen bonding, and the unique reactivity of the carbonyl group due to electron density differences between carbon and oxygen.

Takeaways

• 🧪 Aldhy and ketones are similar molecules with a double-bonded oxygen in their carbon chains, but the position of the double bond differs: aldhy at the end, ketones in the middle.
• 🔍 Aldhy are named similarly to alcohols but end with 'al', while ketones end with 'one', indicating the position of the double-bonded oxygen.
• 📝 For aldhy, the double bond's position is always at the end of the carbon chain, so no number is needed in the name. For ketones, the position is indicated with a number if there's more than one possibility.
• 🔑 The longest carbon chain is counted for naming, and the presence of a double bond in the middle of the chain indicates a ketone.
• 📚 Aldhy and ketones have precedence over alcohols in naming, with the most interesting functional group taking priority.
• 🔬 The polarity of aldhy and ketones is greater than that of alcohols due to the double-bonded oxygen, which is more electronegative.
• 🌡 Despite being more polar, aldhy and ketones have lower boiling and melting points than alcohols because alcohols can form hydrogen bonds.
• 🌟 The double-bonded oxygen in aldhy and ketones is a key feature, making these molecules more reactive due to the electronegative nature of oxygen.
• 📌 The carbon atom bonded to the double-bonded oxygen is slightly positive, which is crucial for understanding reactivity in chemical reactions.
• 📝 When naming complex molecules with multiple functional groups, the naming order of precedence is followed: aldhy, ketones, and then alcohols.
• 🧲 The reactivity of the carbonyl group (double-bonded oxygen with carbon) is significant in chemical reactions, especially when other electronegative groups are present.

Q & A

What is the key difference between aldehydes and ketones in terms of molecular structure?

The key difference lies in the position of the double-bonded oxygen. In aldehydes, the double-bonded oxygen is at the end of the carbon chain, whereas in ketones, it is somewhere in the middle of the carbon chain.

How are aldehydes named in organic chemistry?

Aldehydes are named by counting the longest carbon chain and adding an 'al' ending. Since the double-bonded oxygen is always at the end of the chain, there is no need to specify its position with a number.

What is the naming convention for ketones?

Ketones are named by counting the longest carbon chain and adding an 'one' ending. If the double-bonded oxygen can be in multiple positions within the chain, a number is added to indicate its position.

Why do aldehydes and ketones have higher polarity than alcohols?

Aldehydes and ketones have higher polarity because the double-bonded oxygen is more electronegative, creating a stronger dipole moment within the molecule compared to the single-bonded oxygen in alcohols.

How does the polarity of aldehydes and ketones affect their solubility in water?

Due to their higher polarity, aldehydes and ketones are more soluble in water than alcohols, as they can form stronger dipole-dipole interactions with water molecules.

Why do aldehydes and ketones have lower boiling and melting points than alcohols?

Although aldehydes and ketones are more polar, they have lower boiling and melting points than alcohols because they lack the hydrogen bonding that occurs in alcohols when oxygen is connected to hydrogen.

What is the term for the carbon-oxygen double bond in aldehydes and ketones?

The carbon-oxygen double bond in aldehydes and ketones is referred to as a 'carbonyl' group.

How does the reactivity of the carbonyl group differ from other functional groups?

The carbonyl group is highly reactive due to the electronegativity of the oxygen atom, which pulls electron density away from the carbon atom, making the carbon slightly positive and more susceptible to nucleophilic attack.

What is the precedence in naming when both an aldehyde and an alcohol group are present in a molecule?

When both an aldehyde and an alcohol group are present, the molecule is named as an aldehyde first due to its higher precedence, followed by the alcohol group as a substituent.

Can you provide an example of naming a molecule with both an aldehyde and an alcohol group?

An example would be an octanal molecule with a hydroxy group on carbon 7. It would be named as '7-hydroxy-octanal', with the aldehyde group taking precedence in the name.

What is the significance of the carbonyl group's reactivity in organic chemistry?

The reactivity of the carbonyl group is significant because it can participate in various organic reactions such as nucleophilic addition, oxidation, and reduction, making it a key functional group in many organic transformations.

Outlines

00:00

🧪 Naming and Properties of Aldehydes and Ketones

This paragraph discusses the structural and naming differences between aldehydes (alahh) and ketones. Aldehydes have a double-bonded oxygen at the end of a carbon chain, while ketones have this double bond somewhere in the middle. Aldehydes are named similarly to alcohols but with an 'al' ending, whereas ketones get an 'one' ending. The naming process involves identifying the longest carbon chain and adding a number to indicate the position of the double bond in ketones. The paragraph also highlights that aldehydes get precedence over alcohols in naming. Additionally, it points out that aldehydes and ketones are more polar than alcohols due to the double-bonded oxygen, which makes them more soluble in water but with lower boiling and melting points due to the lack of hydrogen bonding. The reactivity of the carbonyl group (double-bonded oxygen and carbon) is also mentioned, emphasizing the electron-stealing nature of the oxygen atom.

05:04

🌡️ Polarity, Solubility, and Reactivity of Aldehydes and Ketones

The second paragraph delves deeper into the properties of aldehydes and ketones, focusing on their polarity, solubility, and reactivity. It explains that these compounds are more polar than alcohols due to the electronegative nature of the double-bonded oxygen, which attracts electron density away from the carbon. This increased polarity leads to stronger dipole-dipole forces but also results in lower boiling and melting points compared to alcohols, as hydrogen bonding is absent. The paragraph further illustrates the naming conventions for these compounds, emphasizing the need to specify the position of the carbonyl group in ketones. It also touches on the reactivity of the carbonyl group, highlighting how the oxygen's partial negative charge can influence reactions, particularly with negatively charged groups like OH-. The summary concludes with a reminder to keep in mind the naming rules and properties of aldehydes and ketones for future reference.

Keywords

💡Aldhy

Aldhy, short for aldehyde, is an organic compound characterized by a double bonded oxygen at the end of a carbon chain. In the video, it is explained that aldehydes are named similarly to alcohols but with an 'al' ending, and the position of the double bond does not require a number because it is always at the end of the carbon chain. This is crucial for understanding the naming conventions and structural differences between aldehydes and other organic compounds.

💡Ketone

A ketone is an organic compound with a double bonded oxygen located somewhere in the middle of a carbon chain, not at the end. The video script emphasizes that ketones are named with an 'one' ending, and the position of the double bond may require a number to indicate its location on the carbon chain. This distinction is important for differentiating ketones from aldehydes and understanding their structural and naming conventions.

💡Polarity

Polarity in the context of the video refers to the property of a molecule that results from an uneven distribution of electron density, leading to a molecule having opposite ends with partial positive and negative charges. The script explains that aldehydes and ketones are more polar than alcohols due to the electronegative oxygen atom double-bonded to carbon, which makes them more soluble in water but with lower boiling points due to the absence of hydrogen bonding.

💡Boiling Point

The boiling point is the temperature at which a substance changes from a liquid to a gas. In the video, it is mentioned that aldehydes and ketones have lower boiling points than alcohols because, despite being more polar, they lack hydrogen bonding, which is a stronger intermolecular force present in alcohols. This point is used to compare the physical properties of different organic compounds.

💡Melting Point

Melting point is the temperature at which a solid turns into a liquid. The script briefly mentions that, like boiling points, the melting points of aldehydes and ketones are lower than those of alcohols for similar reasons related to polarity and intermolecular forces.

💡Hydrogen Bonding

Hydrogen bonding is a type of dipole-dipole interaction that occurs when a hydrogen atom is bonded to a highly electronegative atom such as oxygen or nitrogen. The video script explains that alcohols have hydrogen bonding due to the presence of an OH group, which results in higher boiling points compared to aldehydes and ketones, which lack such hydrogen bonds.

💡Naming Conventions

Naming conventions in organic chemistry are systematic rules for naming compounds based on their structure. The video script provides examples of how to name aldehydes and ketones, emphasizing the importance of the position of the double bond and the presence of functional groups in determining the name of the compound.

💡Carbonyl Group

The carbonyl group is a functional group consisting of a double bonded oxygen and a carbon atom. The video script describes the carbonyl group as having a high degree of reactivity due to the electronegative oxygen atom pulling electron density away from the carbon, creating a polarized bond. This reactivity is important in organic chemistry for predicting how these compounds will react in various chemical reactions.

💡Electronegativity

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. In the context of the video, the oxygen atom in the carbonyl group is described as being more electronegative, which contributes to the polarity of aldehydes and ketones and influences their reactivity.

💡Reactivity

Reactivity refers to how readily a substance can undergo a chemical reaction. The video script highlights the reactivity of the carbonyl group, particularly how the electronegative oxygen atom influences the carbon's reactivity, making it more susceptible to nucleophilic attack in reactions.

💡Functional Group

A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. The video script discusses the carbonyl group as a functional group in aldehydes and ketones, which dictates their chemical properties and reactivity.

Highlights

Aldhy and ketones are similar molecules with a double-bonded oxygen.

For aldhy, the double-bonded oxygen is at the end of the carbon chain.

Ketones have the double-bonded oxygen somewhere in the middle of the carbon chain.

Aldhy are named similarly to alcohols but with an 'Al' ending.

Ketones are named with an 'ONE' ending.

Aldhy naming does not require a number to indicate the position of the double bond.

Ketones may need a number if there is more than one possibility for the middle position of the double bond.

Naming involves counting the longest carbon chain and adding an 'Al' or 'ONE' ending.

Examples of naming include pentanal and 44-dimethyl pentanal.

Aldhy gets precedence over alcohol in naming.

Naming a compound with both an alcohol and an aldhy focuses on the aldhy.

Ketones are named by numbering the carbon chain to give the double-bonded oxygen the lowest number.

Examples of ketone naming include 2-octanone and 5-octan-2-one.

Aldhy and ketones are more polar than alcohols due to the double-bonded oxygen.

Despite higher polarity, aldhy and ketones have lower boiling and melting points than alcohols due to weaker intermolecular forces.

The double-bonded oxygen in aldhy and ketones makes them more reactive, influencing their reactivity in chemical reactions.

The carbon in aldhy and ketones is slightly more positive due to electron density being pulled by the oxygen.

Understanding the naming and properties of aldhy and ketones is crucial for recognizing their reactivity in chemical processes.

Transcripts

all right next up I want to talk about

alahh and ketones these are similar

molecules in that the most interesting

bit is a double bonded oxygen somewhere

on the chain of carbons for alahh highes

the double bonded oxygen has to be at

the very end of the molecule now these

are all on the right side it could have

just as easily been on the left

side whereas for ketones the double

bonded oxygen is somewhere in the middle

of the carbon chain here it's on the

second carbon looks like it might be on

the fourth one here in any case all

double bonded oxygens mean it's an aldah

or a

ketone alahh are going to be named

similarly to alcohols but they get an Al

ending ketones are going to get an O N E

ending and the only major difference

between the way that you name them is

because alahh are a double bonded oxygen

at the end of a

molecule we don't need a number to tell

us where the double bond in oxygen is

with an alcohol we do need to know where

the O is but not here it has to be on

carbon number one for a ketone a ketone

can be anywhere in the middle and as

long as there's more than one

possibility for the middle you're

probably going to need a number to tell

us where that double bonded oxygen is

let's try some of these e let's try

naming some alahh first here's one let's

count the longest carbon chain and then

we'll add an a L

ending

1 2 3 4 5 that's pent for five it's all

single

bonds and it's an

alahh again we don't need a number to

say where the alahh is because it has to

be at the very beginning has to be on

carbon

one let's try this one down here 1 2 3 4

five oh this is a pent as well it's all

single bonds except of course for the

double bond and oxygen all they all the

carbon carbon bonds are single I should

say

pentan

Al oh I guess it is the same molecule

except here we have two single carbon

chains and that's on carbon 4 so it's 44

dimethyl

pentanal can you guys read that

good and finally I would just want to

point out that the aldhy gets precedence

over alcohol in naming so if you have

both it's an alahh one 2 3 4 5 6 7 8

we're going to call this

octanal and on carbon 7 we have an O

group now when an O group is the most

interesting bit we name it as an alcohol

Octan all for example but here it's not

the most interesting bit it's just

hanging off we call it a

hydroxy 7 hydroxy octanol huh octanal I

should

say let's try this again but with

ketones here we have 1 2 3 4 five carbon

chain

man I must have a thing for five all

carbon carbon single

bonds and we have a double bonded oxygen

but it's in the middle so it's an own a

ketone but that double bonded oxygen

didn't have to be on the second one it

could have just as easily been on the

third one I mean it wasn't but it could

have been which means we have to put a

two here to

show that that's where the Ketone group

is

1 2 3 4 five 6 7 8 I've numbered it so

that the double bonded oxygen gets the

lowest number because it is the highest

precedence here it looks like we have an

o oh looks like we have an

O but it's not all single bonds now now

we have a double bond starting at Carbon

5 you guys remember how to name

alkenes oh man I'm falling apart here o

5 and we need to tell people where the

double bonded oxygen is

2 now notice again I cut off the final e

of in when I added something else to the

end OCT 52 own

beautiful and we'll try this one again

this is supposed to get the lowest

number so 1 2 3 4 5 6 7 8 n ooh a

non all the carbons are single bonds so

it's

nonan and we have to tell people where

the own is it's on carbon 4 nonan 4

own and the other thing is we have a

hydroxy on carbon 8 and an ethyl a two

carbon chain hanging off carbon 7 so

this becomes s

ethyl 8

hydroxy uh and there's no space here

that's all one word seven ethyl 8

hydroxy non and four own nine carbons

all single bonded together double bonded

oxygen on the fourth carbon o group on

the eighth carbon and a two carbon chain

ethyl group on carbon 7 it's exactly

what we've got here what a beautiful

thing the last things I want to point

out

are the properties of alahh and ketones

so number one they're more polar than

the alcohols

are so if you have a three carbon chain

with an O on it and the same three

carbon chain with a double bonded o on

it or even a three carbon chain with a

double bonded o in the middle the fact

that the O is double bonded and it's so

electr negative makes these two

molecules much more polar than this one

I think the polarity of these two uh is

pretty much the same this one may be a

little more polar but it's pretty much

the same the alahh and ketones are more

polar they're more soluble in water etc

etc now even though they're more polar

so they have stronger dipole dipole

forces they have lower boiling and

melting points than the

alcohols because the alcohol has

hydrogen bonding when o is connected to

H you end up with this mysterious

hydrogen bonding inter molecular force

and so of these this one has the highest

boiling point even though it has the

lowest polarity of the

three and the last thing that I want to

point out to you is that the double

bonded oxy like carbon double bonded to

an oxygen has uh very special reactivity

the group itself is called a carbonal

group

and when it's a substituent we're

actually going to call it Oxo the same

way we called o hydroxy in an earlier

thing but what's really important for

you right now is to recognize that this

oxygen steals electron density away from

the carbon the oxygen is actually a

little more negative than you would

expect and the carbon is a little more

positive than you would

expect this is the same

that's Delta minus and Delta plus this

is the same for aldhy and ketones and it

makes a huge deal in reactivity if you

have something that's very negatively

charged like an oh minus

group that o is going to be

attracted to that particular carbon keep

that in mind when you're doing reactions

but for now just remember how to name

alahh and ketones and keep these

properties in mind but best of luck