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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Fish200398 on January 03, 2020, 03:47:49 AM

Title: which organic compound that is acid? what series strongest to weakest acid?
Post by: Fish200398 on January 03, 2020, 03:47:49 AM

1. FCH_2CH_2COOH
2. ClCH_2CH_2COOH
3. BrCH_2CH_2COOH
4. CH_3CHFCOOH

i think all of the compounds are acid. And i think the differences is the halogen attached to carbocylic acid. While all i know in HF HBr HCl, HF is the weakest due to strong electronegativity of  F makes it hard to give proton and HBr is the strongest due to larger radius. but what about this 4 acids what is the series strongest to weakest?

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: AWK on January 03, 2020, 05:23:37 AM

Most of organic acids are classified as weak ones.  You can check K_a (or pK_a)

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: Fish200398 on January 03, 2020, 06:52:49 AM

there is no given Ka, maybe there are other ways to decide it

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: Humr on January 03, 2020, 07:13:35 AM

All are acids and last with nearest F to COOH group is strongest i think. And its because pulling eway electrons from H due to induction effect.

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: AWK on January 03, 2020, 08:18:50 AM

https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/crbacid1.htm

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: hollytara on January 03, 2020, 08:30:19 AM

Ka or Acid Strength 4>1>2>3

pKa is reversed.

F is most electronegative and is most effective at making acid stronger. 
4 has F one atom closer to acid group and therefore also more effective.

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: Fish200398 on January 03, 2020, 10:05:16 AM

in HF HBr HCl HF the series are HBr > HCl > HF. but now in this question the series reverse into F>Cl>Br, why?

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: AWK on January 03, 2020, 11:29:45 AM

https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/2_p-Block_Elements/Group_17%3A_The_Halogens/1Group_17%3A_General_Reactions/The_Acidity_of_the_Hydrogen_Halides

Title: Re: which organic compound that is acid? what series strongest to weakest acid?
Post by: Fish200398 on January 03, 2020, 12:00:28 PM

thanks all