Do you know your functional group transformations from every angle? Alert - you
ID: 1002824 • Letter: D
Question
Do you know your functional group transformations from every angle? Alert - you should know these transformations well for your exams (all the way until the final exam of CH223!)
A) Select the organic starting material (in the context of our study thus far) that is used with PBr3.
alkane
alkene
primary alkyl chloride
primary alcohol
primary alkyl bromide
tertiary alkyl chloride
tertiary alkyl bromide
tertiary alcohol
B) Select the major organic product (in the context of our study thus far) that results from the use of PBr3.
alkene
primary alcohol
primary alkyl chloride
tertiary alcohol
alkane
tertiary alkyl chloride
primary alkyl bromide
tertiary alkyl bromide
C) Select the organic starting material (in the context of our study thus far) that is used with HCl.
tertiary alcohol
primary alcohol
alkane
tertiary alkyl chloride
primary alkyl chloride
alkene
primary alkyl bromide
tertiary alkyl bromide
D) Select the major organic product (in the context of our study thus far) that results from the use of HCl.
primary alkyl bromide
primary alcohol
tertiary alkyl bromide
tertiary alcohol
alkane
tertiary alkyl chloride
primary alkyl chloride
alkene
E) Select the organic starting material (in the context of our study thus far) that is used with Br2.
alkene
tertiary alcohol
tertiary alkyl bromide
tertiary alkyl chloride
alkane
primary alcohol
primary alkyl chloride
primary alkyl bromide
F) Select the major organic product (in the context of our study thus far) that results from the use of Br2.
primary alcohol
primary alkyl bromide
tertiary alkyl bromide
alkene
primary alkyl chloride
alkane
tertiary alkyl chloride
tertiary alcohol
G) Select the reagent needed for a practical reaction with an isoalkane with more than 4 carbons.
HI
HF
PBr3
I2
HCl
F2
HBr
Cl2
Br2
SOCl2, base
H) Select the major organic product resulting from reaction in part G.
primary alkyl bromide
alkane
primary alkyl chloride
tertiary alkyl bromide
alkene
primary alcohol
tertiary alcohol
tertiary alkyl chloride
I) Select the reagent needed for a practical reaction with a primary alcohol without having to heat the reaction to a high temperature.
PBr3
F2
Br2
I2
HCl
HF
Cl2
HBr
Explanation / Answer
- Select the organic starting material (in the context of our study thus far) that is used with PBr3.
Primary alcohol
This reaction is called nucleophilic substitution (SN2), where primary and secondary alcohols (1° and 2° alcohols) are converted into alkyl bromides using PBr3 (phorphorus tribromide). This reaction is catalyzed with common bases like triethylamine, Et3N or pyridine.
- C - OH + PBr3 --------> - C - Br
- Select the major organic product (in the context of our study thus far) that results from the use of PBr3.
Primary alkyl bromide
The result of this reaction is a primary alkyl bromide (if the reaction is carried out with a primary alcohol). If the reaction is carried out with a secondary alcohol, the result is going to be a secondary alkyl bromide.
- Select the organic starting material (in the context of our study thus far) that is used with HCl.
Tertiary alcohol
Alkene
NOTE: This answer depends on what you have studied so far in this subject. Since with HCl two reactions may be performed: with alcohols and alkenes.
Alcohols: this is a halogenation by nucleophilic substitution (SN1) where an alcohol reacts with a hydrogen halide (in this case HCl) to generate an alkyl halide (3° alcohol will produce a tertiary alkyl chloride) and water. Here we have a relative reactivity order: 3° > 2° > 1° > methyl, but when this reaction is carried out with methanol and primary alcohols it will proceed via SN2 mechanism.
(CH3)3 C – OH + HCl --------> (CH3)3 C – Cl
Alkenes: this reaction is called electrophilic addition, when an alkene is treated with a hydrogen halide will produce an alkyl halide (in this case an alkyl chloride), the hydrogen halide can be added to ethylene (CH2 = CH2), secondary and tertiary alkenes; the halide group becomes attached to the carbon with more alkyl substituents.
(CH3)2 C = CH2 + HCl --------> (CH3)3 C – Cl
- Select the major organic product (in the context of our study thus far) that results from the use of HCl.
Tertiary alkyl chloride
Alcohols: with a tertiary alcohol the result will be a tertiary alkyl chloride.
(CH3)3 C – OH + HCl --------> (CH3)3 C – Cl
Alkenes: with the reaction below (isobutene or 2-methylpropene) the result is going to be 2-chloropropane, a tertiary halide.
(CH3)2 C = CH2 + HCl --------> (CH3)3 C – Cl
- Select the organic starting material (in the context of our study thus far) that is used with Br2.
Alkane
This is a radical halogenation of alkanes, where an alkane is treated with Br2, a radical subtitution of R-H occurs to produce an alkyl halide. The relative reactivity order is: 3°> 2°> 1°> methyl. The result is a primary, secondary or tertiary halide, where a tertiary halide is more stable.
(CH3)3 CH + Br – Br -----> (CH3)3 C - Br
- Select the major organic product (in the context of our study thus far) that results from the use of Br2.
Tertiary alkyl bromide
The result of bromination of alkanes is a tertiary bromide as a major product, since thsi is a more stable compound with a higher selectivity.
(CH3)3 CH + Br – Br -----> (CH3)3 C - Br
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