Two more for you-klutzy

[wifi08]

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1)1-chloro-4-methylcyclohexane plus H2O and heat. is it SN1 or E1
the answer is SN1 but why? doesnt the heat make it an elimination rexn?


2) "the exothermic rexn is catalysed by MnO2."
2 H2O2 gives 2 H2O+O2
what increases rate?
answer- raising temp
- increasing surface area of catalyst.
why does raising temp increase rexn? its exothermic unless they mean reverse rexn

 

[PooyaH]

It doesn't matter if a reaction is exothermic or not. Although it is spont. temp. still increases the rate of the reaction!

 

[jdent]

It doesn't matter if a reaction is exothermic or not. Although it is spont. temp. still increases the rate of the reaction!

But why?
and what about the first question?

 

[doc3232]

1)1-chloro-4-methylcyclohexane plus H2O and heat. is it SN1 or E1
the answer is SN1 but why? doesnt the heat make it an elimination rexn?


2) "the exothermic rexn is catalysed by MnO2."
2 H2O2 gives 2 H2O+O2
what increases rate?
answer- raising temp
- increasing surface area of catalyst.
why does raising temp increase rexn? its exothermic unless they mean reverse rexn

You need a base for an elim reaction. Definitely not elim.
It isn't just SN1, it is also SN2. Secondary carbocations aren't that stable, so it will go by SN2 also. heat just speeds up the reaction (this is the answer to both of your questions, so you need to understand this concept).


As previous poster said, increasing temp ALWAYS increase rate as long as proteins are not involved (because they will get denatured).

 

[lazystatefan]

For a reaction to occur, bonds need to be broken and then new bonds are formed. The energy required to break the bonds is the activation energy. In a given sample many molecules will have varying levels of energy, those molecules that have enough energy to overcome the activation energy barrier will proceed with the reaction. Increasing the temperature increases the amount of energy for all of the molecules yielding a higher percentage of molecules with enough energy to overcome the activation energy barrier and thus makes the reaction happen faster.

 

[PreDent2009]

E1 is only an alcohol reacting with a strong acid (H2SO4 or H3PO4 only!). Those are the ONLY E1 reaction conditions. SN1 can be an alcohol with a weaker acid such as HBR or HCL, or it can be a molecule with a leaving group reacting with a weak base such as H20, methanol, ethanol, etc.

When you have strong base like KOCH2CH3, potassium ethoxide or other ionic bases then you consider SN2 vs. E2. First you look at the E2 product, determine the stablity of the alkene, then decide whether it will be SN2 or E2 based on that. If your E2 has 0 carbon-carbon bonds around the double bond, 1 C-C bond around the double bond then you will most likely get SN2, unless you force the reaction with heat and concentrated base. WIth 2 C-C bonds around the double bond you get amixture of E2 and Sn2. 3 C-C, or 4 C-C around the double bond will always be E2.

1)1-chloro-4-methylcyclohexane plus H2O and heat. is it SN1 or E1
the answer is SN1 but why? doesnt the heat make it an elimination rexn?


2) "the exothermic rexn is catalysed by MnO2."
2 H2O2 gives 2 H2O+O2
what increases rate?
answer- raising temp
- increasing surface area of catalyst.
why does raising temp increase rexn? its exothermic unless they mean reverse rexn

 

[xhamburgersamx]

The rate is only dependent on temperature

This is not a Le Chatelier lalalla whatever the heck his name is question, hope t