Physics, Chemistry & Maths Glossary

Browse the glossary using this index

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL

L

Leaving Group

Excellent	TsO^-, NH₃
Very Good	I^-, H₂O
Good	Br^-
Fair	Cl^-
Poor	F^-
Very Poor	HO^-, NH₂^-, RO^-

Leibnitz's Rule

\({d \over {dx}}\left[ {\int_{g(x)}^{h(x)} {f(x,t)dt} } \right] = \int_{g(x)}^{h(x)} {{\partial \over {\partial x}}f(x,t)dt + h'(x)f\{ x,h(x)\} - g'(x)f\{ x,g(x)\} }\)

A simplified situation arises when f depends only on t, making the partial derivative term zero.

\({d \over {dx}}\left[ {\int_{g(x)}^{h(x)} {f(t)dt} } \right] = \int_{g(x)}^{h(x)} {{\partial \over {\partial x}}f(t)dt + h'(x)f\{ x,h(x)\} - g'(x)f\{ x,g(x)\} } \)

\( \Rightarrow {d \over {dx}}\left[ {\int_{g(x)}^{h(x)} {f(t)dt} } \right] = 0 + h'(x)f\{ x,h(x)\} - g'(x)f\{ x,g(x)\} \)

\( \Rightarrow {d \over {dx}}\left[ {\int_{g(x)}^{h(x)} {f(t)dt} } \right] = h'(x)f\{ x,h(x)\} - g'(x)f\{ x,g(x)\}\)

Lucas Test

Test for primary/secondary/tertiary water-soluble (hence small) alcohols using Lucas reagent (solution of conc. HCl + anhydrous ZnCl₂).

Mechanism: S_N1 via carbocation, ROH is converted to RCl. Polar medium helps to stabilise carbocation.

Tertiary alcohol: White turbidity immediately.

Secondary alcohol: White turbidity in 2-3 minutes.

Primary alcohol: White turbidity on heating, not at room temperature.

White turbidity is due to insoluble alkyl halide.