ATAR Notes: Forum

HSC Stuff => HSC Subjects + Help => HSC Science Stuff => Topic started by: joengelman on January 08, 2020, 01:07:37 pm

Title: increasing order of boiling points of hydrocarbons
Post by: joengelman on January 08, 2020, 01:07:37 pm

Hi guys,

what's the order of different hydrocarbons for boiling points? I've found conflicting information online, and I'm just confused. I think its (lowest to highest)

alkanes - alkenes - alkynes - amines - amides - alcohols - carboxylic acid

but wouldn't amides have a higher boiling point than alcohols?

thank you!!

Title: Re: increasing order of boiling points of hydrocarbons
Post by: louisaaa01 on January 08, 2020, 01:53:19 pm

Quote from: joengelman on January 08, 2020, 01:07:37 pm

Hi guys,

what's the order of different hydrocarbons for boiling points? I've found conflicting information online, and I'm just confused. I think its (lowest to highest)

alkanes - alkenes - alkynes - amines - amides - alcohols - carboxylic acid

but wouldn't amides have a higher boiling point than alcohols?

thank you!!

Hi there,

From my studies, I've gathered that it goes (in ascending order): alkanes - alkenes - alkynes - esters - amines - alcohols - carboxylic acids - amides.

You are absolutely correct that amides (-CONH2) have higher boiling points than the corresponding alcohols (-OH). This comes down to the fact that boiling point is dictated by the strength of intermolecular forces. While an O-H bond is more polar than an N-H bond (as oxygen is more electronegative than nitrogen), since amides have more sites for hydrogen bonding than alcohols, they have higher BP’s.

Also just a little point on terminology - hydrocarbons are substances that contain only hydrogen and carbon, so technically from your list, only alkanes, alkenes, and alkynes are considered hydrocarbons!

Hope this helps :)